The besieged Ukrainian port city of Mariupol has been "90% destroyed", according to the local Mayor Vadym Boychenko.
"The sad news is that 90% of the infrastructure in the city is destroyed and 40% is unrecoverable," he told a press conference.
Around 130,000 people remained trapped in the city, he said.
It comes as Ukrainian President Volodymyr Zelensky said the world will recognise the killing of people in the town of Bucha as "genocide".
International journalists over the weekend found bodies, some with their hands bound, in the town of Bucha outside Ukraine's capital after Kyiv's forces retook it from Russia's army.
German Chancellor Olaf Scholz said Russian President Vladimir Putin and his supporters would "feel the consequences" of events in Bucha. Western allies would agree further sanctions against Moscow in coming days, he said, though their timing and reach were not clear.
German Defence Minister Christine Lambrecht said the European Union must discuss banning Russian gas, though other officials urged caution around measures that could touch off a European energy crisis. More than half of Germany's gas came from Russia last year.
France's President Emmanuel Macron suggested sanctions on oil and coal.
Mariupol has been decimated from a month-long bombardment and only the skeletons of residential tower blocks remain on some streets after the shelling.
Ukraine evacuated more than 2,600 people from the city and the region of Luhansk yesterday, Ukrainian Deputy Prime Minister Iryna Vereshchuk said.
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Ukrainian officials were in talks with Russia to allow several Red Cross buses to enter Mariupol, she said and accused Russian forces of blocking Red Cross efforts to reach the city.
Ms Vereshchuk also said that Ukraine currently has around 600 Russian prisoners of war.
The Red Cross abandoned earlier attempts due to security concerns. Russia blamed the charity for the delays.
A team of the International Committee of the Red Cross (ICRC) has not been able to reach Mariupol today to evacuate civilians, a spokesperson said, citing security conditions.
Reuters correspondents saw convoys of armoured vehicles belonging to pro-Russia forces near Mariupol.
Ukraine is preparing for what one army leader said were about 60,000 Russian reservists called in to reinforce its offensive.
A senior US defence official said Russia had repositioned about two-thirds of its forces from around Kyiv, with many consolidating in close ally Belarus where they were expected to be refit, resupplied and be redeployed elsewhere in Ukraine.
British military intelligence also said Russian troops, including contractors from the Wagner private military company, were moving to the east.
Reuters could not independently confirm the claims.
Serhiy Gaidai, the governor of eastern Luhansk region, said Russia was building up forces to break through Ukrainian defences.
"I am urging residents to evacuate. The enemy will not stop, it will destroy everything in its path," he said in comments carried on Ukrainian television.
Eight people were killed and 34 wounded in Russian attacks on two towns in southern Ukraine yesterday
prosecutors in Kyiv said, as the West warned Moscow of more sanctions over civilian killings.
"The Russian armed forces attacked the cities of Ochakiv and Mykolaiv. Shelling damaged residents' homes, vehicles and civilian infrastructure," the Ukrainian prosecutor general said in a statement this morning.
"As a result of enemy shelling, seven residents of Ochakiv were killed and another 20 were injured. In the city of Mykolaiv one person died and 14 people were wounded, among them a child," it added.
The local governor Vitaliy Kim had said that one person had been killed in the attacks on Mykolaiv.
Shelling also hit the eastern city of Kharkiv yesterday causing seven deaths and dozens of injuries, local prosecutors said, while missiles struck near the southern port of Odesa, with Russia saying it had destroyed an oil refinery used by the Ukrainian military.
The Odesa city council said "critical infrastructure facilities" were hit.
Kyiv residents who evacuated to safer regions should wait several more days before returning to Ukraine's capital, Mayor Vitaliy Klitschko said today.
"Firstly, there is currently a round-the-clock curfew in Kyiv region. Secondly, in certain ... towns near Kyiv, it is likely that Russian occupiers left landmines, and there are (likely) a lot of unexploded munitions," he said.
Mr Zelensky said it is "very hard" to negotiate with Russia when "we see what they [have] done in Ukraine".
