By CARA ANNA

LVIV, Ukraine (AP) — Ukrainian officials defiantly rejected a Russian demand that their forces in Mariupol lay down arms and raise white flags Monday in exchange for safe passage out of the besieged strategic port city.

Even as Russia intensified its attempt to pummel Mariupol into surrender, its offensive in other parts of Ukraine has floundered. Western governments and analysts say the broader conflict is grinding into a war of attrition, with Russia continuing to bombard cities.

In the capital, Kyiv, a shopping center in the densely populated Podil district near the city center was a smoldering, flattened ruin after being hit late Sunday by shelling that killed eight people, according to emergency officials. The force of the explosion shattered every window in a neighboring high-rise. Artillery boomed in the distance as firefighters picked their way through the destruction.

Ukrainian authorities also said Russia shelled a chemical plant in northeastern Ukraine, sending toxic ammonia leaking into the air, and hit a military training base in the west with cruise missiles.

The encircled southern city of Mariupol on the Sea of Azov has seen some of the worst horrors of the war, under Russian pounding for more than three weeks, in a brutal assault that Ukrainian and Western officials have called a war crime.

Strikes hit an art school sheltering some 400 people only hours before Russia’s offer to open corridors out of the city in return for the capitulation of its defenders, according to Ukrainian officials.

“They are under the rubble, and we don’t know how many of them have survived,” Ukraine’s President Volodymyr Zelenskyy said. In a video address, he vowed that Ukraine would “shoot down the pilot who dropped that bomb.”

Russian Col. Gen. Mikhail Mizintsev had offered two corridors — one heading east toward Russia and the other west to other parts of Ukraine — in return for Mariupol’s surrender. He did not say what Russia planned if the offer was rejected.

The Russian Ministry of Defense said authorities in Mariupol could face a military tribunal if they sided with what it described as “bandits,” the Russian state news agency RIA Novosti reported.

Ukrainian officials rejected the proposal even before Russia’s deadline of 5 a.m. Moscow time (0200GMT) for a response came and went.

“There can be no talk of any surrender, laying down of arms,” Ukrainian Deputy Prime Minister Irina Vereshchuk told the news outlet Ukrainian Pravda. “We have already informed the Russian side about this.”

Mariupol Mayor Piotr Andryushchenko also quickly dismissed the offer, saying in a Facebook post he didn’t need to wait until the morning deadline to respond and cursing at the Russians, according to the news agency Interfax Ukraine.

The strike on the art school was the second time in less than a week that officials reported an attack on a public building where Mariupol residents had taken shelter. On Wednesday, a bomb hit a theater where more than 1,000 people were believed to be sheltering. At least 130 people were reported rescued Friday, but there has been no update since then.

Mariupol officials said at least 2,300 people have died in the siege, with some buried in mass graves.

City officials and aid groups say Russian bombardment has cut off Mariupol’s electricity, water and food supplies and severed its communications with the outside world, plunging the remaining residents into a chaotic fight for survival.

“What’s happening in Mariupol is a massive war crime,” EU foreign policy chief Josep Borrell said Monday.

Russia’s invasion has rocked the international security order and driven nearly 3.4 million people from Ukraine, according to the United Nations. The U.N. has confirmed 902 civilian deaths in the war but concedes the actual toll is likely much higher. Estimates of Russian deaths vary, but even conservative figures are in the low thousands.

Multiple attempts to evacuate residents from Mariupol and other Ukrainian cities have failed or only partly succeeded, with bombardments continuing as civilians tried to flee.

Some who were able to escape Mariupol tearfully hugged relatives as they arrived by train Sunday in Lviv in western Ukraine.

“Battles took place over every street. Every house became a target,” said Olga Nikitina, who was embraced by her brother as she got off the train. “Gunfire blew out the windows. The apartment was below freezing.”

Mariupol is a key Russian target because its fall would allow Russian forces in southern and eastern Ukraine to unite. But Western military analysts say that even if the city is taken, the troops battling a block at a time for control there may be too depleted to help secure Russian breakthroughs on other fronts.

More than three weeks into the invasion, the two sides now seem to be trying to wear each other down, experts say, with bogged-down Russian forces launching long-range missiles at cities and military bases as Ukrainian forces carry out hit-and-run attacks and seek to sever Russian supply lines.

U.S. Defense Secretary Lloyd Austin said Ukrainian resistance means Russian President Vladimir Putin’s “forces on the ground are essentially stalled.”

Talks between Russia and Ukraine have continued by video conference but failed to bridge the chasm between the two sides, with Russia demanding Ukraine disarm and Ukraine saying Russian forces must withdraw from the whole country.

Zelenskyy has said he would be prepared to meet Putin in person, but Kremlin spokesman Dmitry Peskov said Monday that more progress must be made first. He said that “so far significant movement has not been achieved” in the talks.

U.S. President Joe Biden was expected to talk later Monday with the leaders of France, Germany, Italy and Britain to discuss the war, before heading later in the week to NATO and Group of Seven summits in Brussels and then Poland.

In Ukraine’s major cities, hundreds of men, women and children have been killed in Russian attacks.

Ukraine’s prosecutor general said a Russian shell struck a chemical plant outside the eastern city of Sumy just after 3 a.m. Monday, causing a leak in a 50-ton tank of ammonia that took hours to contain.

Russian military spokesman Igor Konashenkov claimed the leak was a “planned provocation” by Ukrainian forces to falsely accuse Russia of a chemical attack.

Konashenkov also said an overnight cruise missile strike hit a military training center in the Rivne region of western Ukraine. He said 80 foreign and Ukrainian troops were killed, though the figure could not be independently confirmed. Vitaliy Koval, the head of the Rivne regional military administration, confirmed a twin Russian missile strike on a training center there early Monday but offered no details about injuries or deaths.

Britain’s defense ministry said Monday that Ukrainian resistance had kept the bulk of Russian forces more than 25 kilometers (15 miles) from the city center, but that Kyiv “remains Russia’s primary military objective.”

Russian troops are shelling Kyiv for a fourth week now and are trying to surround the capital, which had nearly 3 million people before the war. Kyiv Mayor Vitali Klitschko announced a curfew in the capital from Monday evening to 7 a.m. local time Wednesday, telling residents to stay at home or in shelters.

A cluster of villages on Kyiv’s northwest edge, including Irpin and Bucha, have been all but cut off by Russian forces and are on the verge of humanitarian catastrophe, regional officials said. Associated Press journalists who were in the area a week ago saw bodies in a public park, and not a day goes by without smoke rising from the area.

In another worrying development, Ukraine’s nuclear regulatory agency said radiation monitors around the Chernobyl nuclear power plant, site of the world’s worst meltdown in 1986, have stopped working.

The agency said that, and a lack of firefighters to protect the area’s radiation-tainted forests as the weather warms, could mean a “significant deterioration” in the ability to control the spread of radiation in Ukraine and beyond.

Concerns have been expressed for safety at the shuttered plant since it was seized by Russian forces on Feb. 24, the first day of the invasion. Management at the plant said Sunday that 50 staff members who had been working nonstop since the Russian takeover have been rotated out and replaced.

Earlier this month Russia shelled the working Zaporizhzhia nuclear plant, though no radiation was released.

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Associated Press writer Yuras Karmanau in Lviv, Ukraine, and other AP journalists around the world contributed to this report.

Follow the AP’s coverage of the war at https://apnews.com/hub/russia-ukraine

By CARA ANNA

LVIV, Ukraine (AP) — Russian forces pressed their assault on Ukrainian cities Friday, with new missile strikes and shelling on the capital Kyiv and the outskirts of the western city of Lviv, as world leaders pushed for an investigation of the Kremlin’s repeated attacks on civilian targets, including schools, hospitals and residential areas.

The early morning barrage of missiles on Lviv’s edge was the closest strike yet to the center of the city, which has become a crossroads for people fleeing from other parts of Ukraine and for others entering to deliver aid or fight.

In city after city around Ukraine, hospitals, schools and buildings where people sought safety have been attacked. Rescue workers were still searching for survivors in the ruins of a theater that served as a shelter when it was blasted by a Russian airstrike Wednesday in the besieged southern city of Mariupol.

Ludmyla Denisova, Ukrainain parliament’s human rights commissioner, said Friday that 130 people had survived the theater bombing.

“As of now, we know that 130 people have been evacuated, but according to our data, there are still more than 1,300 people in these basements, in this bomb shelter,” Denisova told Ukrainian television. “We pray that they will all be alive, but so far there is no information about them.”

At Lviv, black smoke billowed for hours after the explosions, which hit a facility for repairing military aircraft near the city’s international airport, only six kilometers (four miles) from the center. One person was wounded, the regional governor, Maksym Kozytskyy, said.

Multiple blasts hit in quick succession around 6 a.m., shaking nearby buildings, witnesses said. The missiles were launched from the Black Sea, but the Ukrainian air force’s western command said it had shot down two of six missile in the volley. A bus repair facility was also damaged, Lviv’s mayor Andriy Sadovyi said.

Lviv lies not far from the Polish border and well behind the front lines, but it and the surrounding area have not been spared Russia’s attacks. In the worst, nearly three dozen people were killed last weekend in a strike on a training facility near the city. Lviv’s population has swelled by some 200,000 as people from elsewhere in Ukraine have sought shelter there.

Early morning barrages also hit a residential building in the Podil neighborhood of Kyiv, killing at least one person, according to emergency services, who said 98 people were evacuated from the building. Kyiv mayor Vitali Klitschko said 19 were wounded in the shelling.

Two others were killed when strikes hit residential and administrative buildings in the eastern city of Kramatorsk, according to the regional governor, Pavlo Kyrylenko.

In Kharkiv, a massive fire raged through a local market after shelling Thursday. One firefighter was killed and another injured when new shelling hit as emergency workers fought the blaze, emergency services said.

The World Health Organization said it has verified 43 attacks on hospitals and health facilities, with 12 people killed and 34 injured.

U.S. Secretary of State Antony Blinken said Thursday that American officials were evaluating potential war crimes and that if the intentional targeting of civilians by Russia is confirmed, there will be “massive consequences.”

The United Nations political chief, Undersecretary-General Rosemary DiCarlo, also called for an investigation into civilian casualties, reminding the U.N. Security Council that international humanitarian law bans direct attacks on civilians.

She said many of the daily attacks battering Ukrainian cities “are reportedly indiscriminate” and involve the use of “explosive weapons with a wide impact area.” DiCarlo said the devastation in Mariupol and Kharkiv ”raises grave fears about the fate of millions of residents of Kyiv and other cities facing intensifying attacks.”

About 35,000 civilians left Mariupol over the previous two days, Kirilenko said Friday.

Hundreds of civilians were said to have taken shelter in a grand, columned theater in the city’s center when it was hit Wednesday by a Russian airstrike. On Friday, their fate was still uncertain, with conflicting reports on whether anyone had emerged from the rubble. Communications are disrupted across the city and movement is difficult because of shelling and fighting.

“We hope and we think that some people who stayed in the shelter under the theater could survive,” Petro Andrushchenko, an official with the mayor’s office, told The Associated Press Thursday. He said the building had a relatively modern basement bomb shelter designed to withstand airstrikes. Other officials said earlier that some people had gotten out.

Video and photos provided by the Ukrainian military showed the at least three-story building had been reduced to a roofless shell, with some exterior walls collapsed. Satellite imagery on Monday from Maxar Technologies showed huge white letters on the pavement outside the theater spelling out “CHILDREN” in Russian — “DETI” — to alert warplanes to the vulnerable people hiding inside.

Russia’s military denied bombing the theater or anyplace else in Mariupol on Wednesday.

In Chernihiv, at least 53 people were brought to morgues over 24 hours, killed amid heavy Russian air attacks and ground fire, the local governor, Viacheslav Chaus, told Ukrainian TV Thursday.

Ukraine’s emergency services said a mother, father and three of their children, including 3-year-old twins, were killed when a Chernihiv hostel was shelled. Civilians were hiding in basements and shelters across the embattled city of 280,000.

“The city has never known such nightmarish, colossal losses and destruction,” Chaus said.

Ukrainian President Volodymyr Zelenskyy said early Friday he was thankful to President Joe Biden for additional military aid, but he would not get into specifics about the new package, saying he did not want Russia to know what to expect. He said when the invasion began on Feb. 24, Russia expected to find Ukraine much as it did in 2014, when Russia seized Crimea without a fight and backed separatists as they took control of the eastern Donbas region.

Instead, he said, Ukraine had much stronger defenses than expected, and Russia “didn’t know what we had for defense or how we prepared to meet the blow.”

In a joint statement, the foreign ministers of the Group of Seven leading economies accused Russian President Vladimir Putin of conducting an “unprovoked and shameful war,” and called on Russia to comply with the International Court of Justice’s order to stop its attack and withdraw its forces.

Both Ukraine and Russia this week reported some progress in negotiations. Zelenskyy said he would not reveal Ukraine’s negotiating tactics.

“Working more in silence than on television, radio or on Facebook,” Zelenskyy said. “I consider it the right way.”

Putin spoke by phone Friday with German Chancellor Olaf Scholz, who urged the Russian president to agree to an immediate cease-fire and called for an improvement to the humanitarian situation, a spokesman for Scholz said.

In a statement about the call, the Kremlin said Putin told the German chancellor that Ukraine had “unrealistic proposals” and was dragging out negotiations. The Kremlin also said it was evacuating civilians, and accused Ukraine of committing war crimes by shelling cities in the east.

While details of Thursday’s talks were unknown, an official in Zelenskyy’s office told the AP that on Wednesday, the main subject discussed was whether Russian troops would remain in separatist regions in eastern Ukraine after the war and where the borders would be.

The official, speaking on condition of anonymity to discuss the sensitive talks, said Ukraine was insisting on the inclusion of one or more Western nuclear powers in the negotiations and on legally binding security guarantees for Ukraine.

In exchange, the official said, Ukraine was ready to discuss a neutral military status.

Russia has demanded that NATO pledge never to admit Ukraine to the alliance or station forces there.

The fighting has led more than 3 million people to flee Ukraine, the U.N. estimates. The death toll remains unknown, though Ukraine has said thousands of civilians have died.

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Associated Press writer Yuras Karmanau in Lviv, Ukraine, and other AP journalists around the world contributed to this report.

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Follow the AP’s coverage of the war at https://apnews.com/hub/russia-ukraine