The humanitarian situation was deteriorating in besieged Ukrainian cities under relentless Russian bombardment on Sunday.
In an apparent escalation of the conflict, Moscow on Saturday claimed it had used hypersonic missiles in Ukraine in what would be the first combat use of the next-generation weapons.
It said on Sunday that it had again fired its newest Kinzhal hypersonic missiles in Ukraine, destroying a fuel storage site in the country's south.
Thousands of people have been evacuated from besieged cities but Russian shelling was blocking efforts to deliver humanitarian supplies, President Volodymyr Zelenskyy said Sunday.
Aid agencies have warned they are struggling to reach hundreds of thousands of people trapped by the invading Russian forces.
A total of 6,623 people were evacuated on Saturday along humanitarian corridors, including 4,000 from the devastated southern city of Mariupol, Mr Zelenskyy said in his latest video address.
Russia said Saturday its forces had broken through the defences of the besieged port and were now inside the war-torn city, which has been under relentless bombardment.
Mr Zelenskyy said the siege of Mariupol would go down in history as a war crime.
Evacuation of civilians from secure corridors continues in Mariupol, Ukraine on 18 March 2022. Source: Anadolu / Anadolu Agency/Anadolu Agency via Getty Images
Russian shelling also heavily damaged the Azovstal metallurgical plant in Mariupol, one of the largest in Europe, Ukrainian officials said.
"The economic losses for Ukraine are immense," tweeted lawmaker Lesia Vasylenko, who posted a video showing thick columns of smoke rising from an industrial complex.
In Mariupol, rescuers were still searching for hundreds of people trapped under the wreckage of a bombed theatre where more than 1,000 people had been seeking shelter when it was struck on Wednesday.
"This is no longer Mariupol, it's hell," said resident Tamara Kavunenko, 58. "The streets are full with the bodies of civilians."
Satellite imagery of the Mariupol Drama Theatre which was bombed on 16 March. Credit: Maxar/DigitalGlobe/Getty Images
"In Chernigiv, indiscriminate artillery shelling in residential neighbourhoods continues, killing dozens of civilians, children and women," mayor Vladislav Atroshenko said on television.
"The city is suffering from an absolute humanitarian catastrophe."
Dire situation
Aid agencies are struggling to reach people trapped in cities ringed by Russian forces, the UN's World Food Programme said Saturday.
"The challenge is to get to the cities that are encircled or about to be encircled," emergency coordinator Jakob Kern told AFP, describing the situation as "dire".
More than 3.3 million refugees have fled Ukraine, but many people have remained trapped, including "hundreds of thousands of women and children. They cannot come out and we cannot reach them," he added.
In western Ukraine, Russia claimed Saturday it had used Kinzhal (Dagger) hypersonic missiles to destroy an arms depot.
Military analyst Pavel Felgenhauer however suggested the use of the missiles would change little on the ground.
"Fundamentally this does not change anything on the battlefield, but it gives a certain psychological and propaganda effect to scare everyone," he told AFP.
Despite their progress entering the centre of Mariupol, Russian forces have met fierce resistance and been stalled outside Kyiv and several other cities in the east, making them vulnerable to Ukrainian attacks against supply lines.
