US President Joe Biden branded Vladimir Putin a "war criminal"on Wednesday as the Russian leader's onslaught in Ukraine claimed more civilian lives, and a theatre where "hundreds" were sheltering was destroyed by bombing.
Biden's rebuke -- his sharpest yet -- came after Ukraine's leader Volodymyr Zelensky made a searing appeal for help to the US Congress and the president himself, who responded by pledging $1 billion in new weapons to fight Russia's invading army.
Officials in the port city of Mariupol were struggling to count the dead at the Drama Theatre, where thick smoke rose from the rubble of the building that had the word "children" painted in large Russian letters on the ground outside.
It was the latest in a litany of assaults on civilians across Ukraine since Putin invaded on February 24 that has included homes, hospitals, ambulances and food queues.
"I think he is a war criminal," Biden told reporters of his Russian counterpart, the first time he has used the phrase.
Biden's spokesperson added that he had spoken "from his heart" -- but the Kremlin quickly punched back, calling the comment "unacceptable and unforgivable on the part of the head of a state, whose bombs have killed hundreds of thousands of people around the world."
So far the destruction that has marked other cities has been halted outside Kyiv.
But dull booms echoed across the capital's deserted streets Wednesday, with only an occasional vehicle passing through sandbagged checkpoints, and very few permits granted to break its latest curfew.
Kyiv has been emptied of around half of its 3.5 million people.
"It's worrying, of course. It's war after all. But we try to stay calm, we won't allow panic," said Eduard Demenchuk, a private-security employee in his 50s, was among those who have stayed.
"If need be, we will take arms and will stand to defend the city," he told AFP by telephone, after stocking up on groceries.
'Destruction of hope'
The attack on the theatre in Mariupol is the latest atrocity in the southern city, which has been besieged for weeks, with more than 2,000 people killed so far.
Mariupol city authorities said Russia "purposefully destroyed" the theatre, though Moscow blamed Ukrainian forces for the blast.
Efforts to establish the number of casualties were hampered by nearby shelling.
President Zelensky gave no further details in his regular evening address, saying only "my heart is breaking seeing what Russia is doing to our people, to our Mariupol."
Also on Wednesday at least 15 civilians were killed in the northern city of Chernihiv.
Ten of them died while queueing to collect bread. Another five, including three children, were killed when Russian forces shelled a residential building.
As the civilian toll climbed, the World Health Organization warned that Ukraine's health system was "teetering on the brink."
"This is about the destruction of hope ... This is the most basic of human rights and it has been directly denied," WHO official Michael Ryan said in Geneva.
The conflict has already sent more than three million Ukrainians fleeing across the border, many of them women and children.
Ukraine authorities said 103 children have been killed since the invasion began.
The New Arab is providing live updates of the latest on the ground and additional analysis on the conflict's significance.
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