Ukraine on Saturday called on civilians in the eastern Luhansk region to flee from Russian shelling, after officials said at least 52 civilians trying to evacuate by rail from a neighbouring region were killed in a missile attack. Air raid sirens rang out across much of the east of Ukraine on Saturday morning, officials said, as Luhansk Governor Serhiy Gaidai urged people in a televised address to leave as Russia was amassing forces for an offensive.

President Volodymyr Zelenskiy called for a “firm global response” to Friday’s missile attack on a train station crowded with women, children and the elderly in Kramatorsk, in the Donetsk region. The city mayor estimated 4,000 people were gathered there at the time. Russia’s defence ministry denied responsibility for the attack, saying in a statement, “The missiles that struck the station were used only by Ukraine’s military and that Russia’s armed forces had no targets assigned in Kramatorsk on Friday. All statements by the Ukrainian authorities on the attack were provocations,” it said.