People hold placards and blood splattered fake-babies at a protest in support of Ukraine on Whitehall in central London on Saturday. AFP

Six weeks into Russia's invasion, Moscow has shifted its focus to eastern and southern Ukraine after stiff resistance ended plans to swiftly capture Kyiv.

Civilians trapped in the region have faced brutal conditions, and EU leaders met President Volodymyr Zelensky in a show of support as news emerged of the devastating attack on Kramatorsk's station. The 52 victims included five children.

With thousands killed in fighting and more than 11 million fleeing their homes or the country, Zelensky said the strike marked a fresh atrocity and called called for a "firm global response" to the bloody incident.

"This is another Russian war crime for which everyone involved will be held accountable," he said in a video message.

"World powers have already condemned Russia's attack on Kramatorsk. We expect a firm global response to this war crime."
Zelensky later said he remained open to talks with Russia to resolve the conflict.

US President Joe Biden accused Russia of being behind a "horrific atrocity" in the de facto capital of the Ukrainian-controlled Donetsk region, and France condemned the strike as a "crime against humanity."

Moscow denied responsibility for the rocket attack on Friday morning, which killed 52 and injured a further 109 people, according to the latest official count.

The Ukrainian president said the bombing had been reported in Russia before the missiles had even landed and called for more weaponry to counter Moscow's aggression.

"I am sure that the victory of Ukraine is just a matter of time, and I will do everything to reduce this time," he added.

Minibuses assembled at a church in Kramatorsk to collect shaken evacuees on Saturday. Almost 80 people, most of them elderly, took shelter overnight in the building, not far from the targeted station.

"There were around 300 to 400 people who rushed here after the strike," Yevgeny, a member of the Protestant church, told AFP.

"They were traumatised. Half of them ran to shelter in the cellar, others wanted to leave as soon as possible. Some were evacuated by bus in the afternoon (on Friday)."

The station in Kramatorsk was being used as the main evacuation hub for refugees from the parts of the eastern Donbas region still under Ukrainian control.

AFP reporters at the station saw the remains of the missile tagged in white paint with the words "for our children" in Russian. The expression is frequently used by pro-Russian separatists in reference to their losses since the start of the first Donbas war in 2014.

The governor of Donetsk claimed a missile with cluster munitions was used in the attack, according to remarks published by the Interfax news agency.

Agence France-Presse