Ukrainian rescue workers have recovered 15 bodies after Russian Uragan rockets hit a five-story apartment block, collapsing the building in the eastern Donetsk region, officials said.
More than 20 people may still be trapped in the wreckage, the local branch of the emergency service in the town of Chasiv Yar said on Facebook.
Emergency workers late on July 10 pulled a man who had been trapped for almost 24 hours out of the rubble, bringing to six the number found alive. The man was rushed to a hospital after being pulled out by rescuers, who earlier said they were in contact with at least three people trapped under the ruins.
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Ukrainian President Volodymyr Zelenskiy said the attack on Chasiv Yar has prompted him to including the topic of war crimes on his schedule in the coming week.
"Since the beginning of this invasion, Ukrainian law enforcement officers have been doing everything necessary to record the crimes of the occupiers and to collect evidence," he said in a video message on July 10.
He said the negotiations he plans will "contribute to the punishment of Russian war criminals."
Pavlo Kyrylenko, the head of the Donetsk military administration, said the attack took place late on July 9.
Chasiv Yar is a town of about 12,000 about 20 kilometers southeast of Kramatorsk, a city that has recently has been a target of Russian forces.
Andriy Yermak, chief of staff to Ukraine's president, said the strike was "another terrorist attack" and that Russia should be designated as a "state sponsor of terrorism" as a result.
The rocket assault on Chasiv Yar is the latest in a recent burst of high-casualty Russian attacks on civilian structures in Ukraine.
At least 19 people died when a Russian missile hit a shopping mall in the city of Kremenchuk in late June. Earlier this month, 21 people were killed when an apartment building and recreational area came under rocket fire in the southern Odesa region.
Russia -- which says it is conducting a "special military operation" to demilitarize Ukraine -- denies targeting civilians in the war. There was no comment on the strike on Chasiv Yar at a Russian Defense Ministry briefing on July 10.
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Search And Rescue Ongoing After Russian Rockets Hit Apartment Blocks In Ukraine
Multiple rocket attacks were also reported in Ukraine's second-largest city, Kharkiv, not far from the Russian border.
Rockets, fired in the early hours of July 10, hit a school, a private house, and a children's sanatorium, partially destroying the buildings, the Kharkiv prosecutor's office said. A 62-year-old man was wounded in the attacks, it said in a Telegram post.
Ukrainian officials said Russian forces attacked areas near the eastern town of Slovyansk on July 10, but were forced to withdraw.
Serhiy Hayday, the governor of eastern Luhansk region, said Russian troops were gathering in the village of Bilohorivka, about 50 kilometers east of Slovyansk.
"The enemy is...shelling the surrounding settlements, carrying out air strikes, but it is still unable to quickly occupy the entire Luhansk region," Hayday said on Telegram.
"During the last night alone, the Russians launched seven artillery barrages and four rocket strikes," he added.
The Ukrainian military General Staff said in its daily summary that attacks were reported in several cities and towns in eastern and southern Ukraine.
Donetsk and Luhansk make up the Donbas region, where Moscow-backed separatists have fought Ukrainian forces since 2014.
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Last week, Russian forces captured the city of Lysychansk, the last major stronghold of Ukrainian resistance in Luhansk.
Meanwhile, the situation in the southern region of Kherson has become more dangerous.
Serhiy Khlan, deputy chief of the Kherson regional council in exile, said Ukrainian troops struck a military unit in the southern city of Kherson, setting it on fire.
Serhiy Bratchuk, the head of the Odesa regional administration, said on Telegram that Ukrainian forces "struck the occupiers' base in the Kherson region."
Russian air-defense systems were activated in Kherson on July 10, TASS reported, adding that four explosions were heard and smoke was seen in the central part of the city.
Ukrainian Deputy Prime Minister Iryna Vereshchuk urged civilians to evacuate the city and the Kherson region.
"It's clear there will be fighting, there will be artillery shelling...and we therefore urge (people) to evacuate urgently," she said on July 10 on national television.
She could not say when exactly the counteroffensive would happen.
The Kherson region includes the city of Kherson, which before the war had a population of nearly 300,000. It is not known how many of the city's residents remained after Ukraine lost control of most of the Kherson region in the early weeks of the war.
Meanwhile, Defense Minister Oleksiy Reznikov said on July 10 that advanced U.S. long-range multiple-launch rocket systems had already made a "huge difference" on the battlefield.
Ukraine currently has nine of the high-mobility artillery rocket systems (HIMARS) and similar systems provided by the U.S. and allies, Security Council Secretary Oleksiy Danilov said earlier this week.
The United States announced on July 8 that it would be sending four more. It said that would bring the number of HIMARS sent by Washington to 12.
Reznikov told The Times in an article published on July 10 that Zelenskiy has instructed the Ukrainian military to retake the occupied southern territories.
"We understand that politically it is very necessary for our country," he told the British newspaper. "The president has instructed the supreme military commander to develop plans."