As many as 60 people are feared to have been killed when a bomb struck a village school in eastern Ukraine, the regional governor said on Sunday while Russian forces continued shelling the last holdout of Ukrainian resistance in the ruined southeastern port of Mariupol.
Luhansk region governor Serhiy Gaidai said the school in Bilohorivka, where about 90 people were sheltering, was hit on Saturday by a Russian bomb, setting it ablaze.
"Thirty people were evacuated from the rubble, seven of whom were injured. Sixty people were likely to have died," Mr Gaidai wrote on the Telegram messaging app, adding that two bodies had been found.
Reuters could not immediately verify his account. There was no response from Moscow to the report.
Ukraine and its Western allies have accused Russian forces of targeting civilians in the war, something that Moscow denies.
In Mariupol, the deputy commander of the Azov regiment holed up in the sprawling Azovstal steel plant pleaded with the international community to help evacuate wounded soldiers.
"We will continue to fight as long as we are alive to repel the Russian occupiers," Captain Sviatoslav Palamar told an online news conference.
As the fighting, now in its third month, raged on, with authorities in the eastern Kharkiv region reporting more casualties of Russian shelling, leaders of the Group of Seven industrial nations vowed on Sunday to deepen Russia's economic isolation and "elevate" a campaign against Kremlin-linked elites.
US president Joe Biden and other G7 leaders held a video call with Ukrainian president Volodymyr Zelenskiy in a show of unity ahead of Russia's Victory Day celebrations on Monday.
The G7 said it was committed to phasing out or banning Russian oil and denounced president Vladimir Putin's invasion of Ukraine.
"His actions bring shame on Russia and the historic sacrifices of its people," the group said in a statement, referring to Soviet Russia's role in defeating Nazi Germany 77 years ago.
Washington also unveiled another round of sanctions targeting more executives and businesses as part of a broad effort to isolate Russia and limit resources being used to advance the war. It also announced a new policy of visa restrictions on more than 2,500 Russian military officials and Russian-backed forced in Ukraine, according to a State Department fact sheet.
In the Ukrainian-controlled city of Zaporizhzhia, about 230km northwest of Mariupol, dozens of people who had fled the city and nearby occupied areas waited to register in a car park set up for evacuees.
"There's lots of people still in Mariupol who want to leave but can't," said history teacher Viktoria Andreyeva, 46, who said she had only just reached the city after leaving her bombed home in Mariupol with her family in mid-April.
The air feels different here, free.
"The air feels different here, free," she said in a tent where volunteers offered food, basic supplies and toys to the evacuees, many travelling with small children.
In an emotional address on Sunday for Victory Day, when Europe commemorates Nazi Germany's formal surrender to the Allies in World War Two, Mr Zelenskiy said that evil had returned to Ukraine with the Russian invasion, but his country would prevail.
Putin says that he launched a "special military operation" on February 24th to disarm Ukraine and rid it of anti-Russian nationalism fomented by the West. Ukraine and its allies say Russia launched an unprovoked war.
Mariupol is key to Moscow's efforts to link the Crimean Peninsula, seized by Russia in 2014, and parts of the eastern regions of Luhansk and Donetsk that have been controlled by Russia-backed separatists since then.
Russian deputy prime minister Marat Khusnullin said on Telegram that he visited Mariupol on Sunday, the country's most senior government figure to set foot in the city after weeks of Russian bombardment.
Khusnullin, who is in charge of construction and urban development, visited the commercial port there and said it should serve to bring in building materials to restore the city, according to the Russian defence ministry's Zvezda TV channel.
A number of Western officials, including US first lady Jill Biden, Canadian prime minister Justin Trudeau, a German parliament head and the Norwegian foreign minister arrived in Ukraine on Sunday in a show of support. A team of US diplomats also arrived in Kyiv for the first time since the invasion.
Putin sent Victory Day messages to separatist leaders in Luhansk and Donetsk, saying Russia was fighting shoulder to shoulder with them and likening their joint efforts to the war against Nazi Germany. "Victory will be ours," Putin said, according to a Kremlin press release on Sunday.
Russia's efforts have been stymied by logistical and equipment problems and high casualties in the face of fierce resistance.
Putin will preside on Monday over a parade in Moscow's Red Square of troops, tanks, rockets and intercontinental ballistic missiles, making a speech that could offer clues on the future of the war.
The Russians "have nothing to celebrate tomorrow," the US ambassador to the United Nations, Linda Thomas-Greenfield, said on CNN. "They have not succeeded in defeating the Ukrainians. They have not succeeded in dividing the world or dividing Nato."