Rescue workers searched for survivors Thursday in the ruins of a theater blown apart by a Russian airstrike in the besieged city of Mariupol, while scores of Ukrainians across the country were killed in ferocious urban attacks on a school, a hostel and other sites.

Hundreds of civilians had been taking shelter in the grand, columned theater in central Mariupol after their homes were destroyed in three weeks of fighting in the southern port city of 430,000.

More than a day after the airstrike, there were no reports of deaths. With communications disrupted across the city and movement difficult because of shelling and other fighting, there were conflicting reports on whether anyone had emerged from the rubble.

“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. He said the building had a relatively modern basement bomb shelter designed to withstand airstrikes. Video and photos provided by the Ukrainian military showed that the at least three-story building had been reduced to a roofless shell, with some exterior walls collapsed.

Other officials had said earlier that some people had gotten out. Ukraine’s ombudswoman, Ludmyla Denisova, said on the Telegram messaging app that the shelter had held up.

Satellite imagery on Monday from Maxar Technologies showed huge white letters on the pavement in front of and behind the theater spelling out “CHILDREN” in Russian — “DETI” — to alert warplanes to those inside.

Across the city, snow flurries fell around the skeletons of burned, windowless and shrapnel-scarred apartment buildings as smoke rose above the skyline.

“We are trying to survive somehow,” said one Mariupol resident, who gave only her first name, Elena. “My child is hungry. I don’t know what to give him to eat.”

She had been trying to call her mother, who was in a town 50 miles (80 kilometers) away. “I can’t tell her I am alive, you understand. There is no connection, just nothing,” she said.

Cars, some with the “Z” symbol of the Russian invasion force in their windows, drove past stacks of ammunition boxes and artillery shells in a neighborhood controlled by Russian-backed separatists.

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

The strike against the theater was part of a furious bombardment of civilian sites in multiple cities over the past few days.

In the northern city of Chernihiv, at least 53 people had been brought to morgues over the past 24 hours, killed amid heavy Russian air attacks and ground fire, the local governor, Viacheslav Chaus, told Ukrainian TV on 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 officials said 10 people were killed Wednesday while waiting in a bread line in Chernihiv. An American man was among them, his sister said on Facebook.

At least 21 people were killed when Russian artillery destroyed a school and a community center before dawn in Merefa, near the northeast city of Kharkiv, according to Mayor Veniamin Sitov. The region has seen heavy bombardment in a bid by stalled Russian forces to advance.

In eastern Ukraine, a municipal pool complex where pregnant women and women with children were taking shelter was also hit Wednesday, according to Pavlo Kyrylenko, head of the Donetsk regional administration. There was no word on casualties in that strike.

Ukrainian President Volodymyr Zelenskyy called for more help for his country in a video address to German lawmakers, saying thousands of people have been killed, including 108 children. He also referred to the dire situation in Mariupol, saying: “Everything is a target for them.”

The address began with a delay because of a technical problem caused by an attack close to where Zelenskyy was speaking, Bundestag deputy speaker Katrin Goering-Eckardt said.

Zelenskyy’s office said Russian airstrikes hit the Kalynivka and Brovary suburbs of the capital, Kyiv. Emergency authorities in Kyiv said a fire broke out in a 16-story apartment building hit by remnants of a downed Russian rocket, and one person was killed.

Zelenskyy said he was thankful to U.S. 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.”

At a Thursday meeting of the U.N. Security Council, World Health Organization Director-General Tedros Adhanom Ghebreyesus said the WHO has verified 43 attacks on hospitals and health facilities, with 12 people killed and 34 injured. Tedros said disruption to hospital services now poses an extreme risk to people with serious illnesses and “the lifesaving medicine we need right now is peace.”

In a joint statement, the foreign ministers of the Group of Seven leading economies accused 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.

Russian law enforcement, meanwhile, announced the first known criminal cases under a new law that allows for 15-year prison terms for posting what is deemed to be “false information” about the war. Among those charged was Veronika Belotserkovskaya, a Russian-language cookbook author and blogger living abroad.

One day after Biden called Russian President Vladimir Putin a “war criminal,” U.S. Secretary of State Antony Blinken said American officials were evaluating and documenting potential war crimes committed by Russia in Ukraine. Blinken said the intentional targeting of civilians would amount to a war crime and that there will be “massive consequences” for any such crimes that are confirmed.

Both Ukraine and Russia this week reported some progress in negotiations. Kremlin spokesman Dmitry Peskov said Thursday that some negotiators were breaking into working groups, “but there should be contacts today.”

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.”

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.