A grave with at least two civilian bodies has been found in Buzova village near Kyiv, a Ukrainian official says, the latest reported grave after Russian forces withdrew from areas north of the capital to focus their assault on the east.

Taras Didych, head of the Dmytrivka community that includes Buzova, told Ukrainian television earlier that a grave with dozens of bodies had been found in a ditch near a petrol station.

“Right now, as we are speaking, we are digging out two bodies of villagers, who were killed. Other details I cannot disclose,” Didych told Reuters by telephone.

“There are other people who we cannot find. They could be in different places, but this doesn’t lessen the pain of the loss of loved ones.”

Mounting civilian casualties have triggered widespread international condemnation and new sanctions, in particular over hundreds of deaths in the town of Bucha, to the north-west of Kyiv that until just over a week ago was occupied by Russian forces.

Moscow has rejected accusations of war crimes by Ukraine and Western countries and denied targeting civilians.

Russia has failed to take any major cities since invading on February 24 but Ukraine says Russia is gathering its forces in the east for a major assault and has urged people to flee.

Russia is seeking to establish a land corridor from Crimea, which it annexed in 2014, and the eastern Donbas region, which is partly held by Moscow-backed separatists, Britain’s defence ministry said.

Russian armed forces are also looking to strengthen troop numbers with personnel discharged from military service since 2012, it said in a regular intelligence update on Sunday.

Satellite images released by private US firm Maxar dated April 8 showed armoured vehicles and trucks in a military convoy moving south toward Donbas through a town some 100 kilometres east of Kharkiv.

Some cities in the east are under heavy shelling with tens of thousands of people unable to evacuate.

President Volodymyr Zelensky said in an address late on Saturday Russia’s use of force was “a catastrophe that will inevitably hit everyone”.

Ukraine was ready to fight for victory while looking for a diplomatic end to the war, he said, and renewed his appeal to Western allies for a total ban on Russian energy products and more weapons for Ukraine.

British Prime Minister Boris Johnson met Mr Zelensky in Kyiv on Saturday and pledged armoured vehicles and anti-ship missile systems, alongside support for World Bank loans and Britain’s commitment to move away from using Russian fossil fuels.

The European Union, which on Friday banned Russian coal imports among other products, has yet to touch oil and gas imports from Russia.

Ukraine late on Saturday announced a full ban on imports from Russia, its key trading partner before the war with some $US6 billion in annual imports.

Mr Johnson was the latest foreign leader to visit Kyiv after Russian forces pulled back from the area, marking a return to some degree of normality for the capital. Italy said it planned to re-open its embassy this month.

But in the east, calls by Ukrainian officials for civilians to flee gained more urgency after a missile struck a train station in the city of Kramatorsk in the Donetsk region, packed with women, children and the elderly trying to get out.

Ukrainian officials said more than 50 people were killed in Friday’s strike.

Russia has denied responsibility, saying the missiles used in the attack were only used by Ukraine’s military. The United States says it believes Russian forces were responsible.

Residents of the region of Luhansk would have nine trains on Sunday to get out on, the region’s governor, Serhiy Gaidai, wrote on the Telegram message service.

-Reuters