At least 60 people died after a Russian airstrike targeted a school in the Luhansk region, Ukrainian authorities said Sunday.
Just hours later, the leader of the G-7 group of industrialized nations announced they were imposing new sanctions on Russia after a videoconference with Ukrainian President Volodymyr Zelenskyy.
Two bodies have been recovered so far after an airstrike on the school in Bilogorivka, the region's governor Serhiy Haidai announced on his Telegram channel on Sunday.
"Probably all 60 people who are still under the rubble of the building are dead," he added.
According to Haidai, 90 people had sought shelter from the attacks in the school building. The bombing caused a fire to break out in the school, which then led to the building's collapse.
Emergency services were able to rescue 30 people, seven of whom were injured, the governor said.
Bilogorivka is an urban settlement about 10 kilometers (6.2 miles) west of Lysychansk, which is under heavy Russian bombardment.
After several days without significant progress, Russian troops have now regained ground in their attacks in Ukraine's far eastern Donbass region, according to Ukrainian sources.
Luhansk and Donetsk together make up the Donbass region, where Russia has refocused its attacks since failing to make advances near the capital Kyiv and in other parts of Ukraine.
Pro-Russian separatists have been battling Ukrainian government forces in the region since 2014.
In the heavily besieged southeastern city of Mariupol, Ukrainian units were continuing to hold out at the Azovstal steel plant. With air and artillery support, Russian troops are continuing their assault attempts there.
Kyiv hopes that the wounded and soldiers can soon be rescued and Zelenskyy said on Saturday evening that a new phase of the evacuation is being prepared.
Regardless of their extremely difficult situation, the soldiers do not want to give up. "Surrender is not an option for us because Russia has no interest in our lives," Illya Samoylenko of the Azov Regiment told an online news conference on Sunday from inside the plant.
On Saturday, all civilian women, children and elderly people who have been taking refuge in the steelworks left the facility, Ukrainian Deputy Prime Minister Iryna Vereshchuk said.
In another of the key battlegrounds of the war, Russian forces said they had shot down two Ukrainian bombers and a helicopter around Snake Island, around 35 kilometers off the coast, south of the city of Odessa.
The Ukrainian military said it had sunk at least one Russian boat and showed a video purporting to be the shooting down of a Russian helicopter over the island.
The Ukrainian military said the Russians were on the defensive in the north of the Kharkiv region.
In Odessa, the administration of the port city reported that more than 250 apartments were damaged by Russian attacks. There was initially no mention of possible casualties.
Russian troops, meanwhile, have captured the ruined small town of Popasna after weeks of fighting, according to Ukrainian sources.
"Unfortunately, our troops have actually retreated somewhat from Popasna because the town was shelled for more than two months," Luhansk Governor Serhiy Haidai said in a television interview on Sunday, according to the UNIAN news agency.
The military developments could not be independently verified.
British intelligence said on Sunday that Moscow had been forced to send high-ranking officers to the front line of the war due to the heavy losses among its forces in Ukraine.
"The forward deployment of commanders has exposed them to significant risk," said the intelligence assessment released by the Ministry of Defense.
In an emotional video address from the heavily damaged Kyiv suburb of Borodyanka, Zelenskyy drew parallels between the German invasion in World War II and the current Russian invasion.
"A bloody reconstruction of Nazism was organized in Ukraine," Zelenskyy said in a black-and-white video shown in front of the rubble of an apartment building.
"A fanatical repetition of this regime. Its ideas, actions, words and symbols. Maniacal detailed reproduction of its atrocities and 'alibi,' which allegedly give an evil sacred purpose."
The anniversary of the end of World War II in Europe 77 years ago was also the subject of a visit to Kyiv by German Bundestag President Barbel Bas on Sunday.
She is the most important German politician to visit Ukraine since the beginning of the Russian invasion, as Kyiv and Berlin tried to put a row over official visits behind them.
Bas laid wreaths at the Tomb of the Unknown Soldier and at the Babyn Yar memorial to the murdered Ukrainian Jews on behalf of the German Bundestag. She was accompanied by her Ukrainian counterpart Ruslan Stefantschuk.
Bas called for peace in Ukraine and said "for me, it is a special day that should not only be commemorated, but also serve reconciliation."
Canadian Prime Minister Justin said on Twitter that he visited the city of Irpin close to Kyiv on Sunday.
"Canada will always stand shoulder to shoulder with Ukraine," he wrote during the unannounced trip.
U.S. first lady Jill Biden also made a brief visit to the country on Sunday. She traveled from Slovakia, where she had been visiting border areas and talking with refugees.
In the Ukrainian city of Uzhhorod, she met Olena Zelenska, Zelenskyy's wife. The two first ladies embraced and Jill Biden gave her Ukrainian counterpart a bouquet of flowers.