Ukraine is ready for a tough battle with Russian forces amassing in the east of the country, President Volodymyr Zelensky said on Saturday, a day after a missile attack in the east that officials said killed more than 50 civilians trying to evacuate.

Air-raid sirens sounded in cities across eastern Ukraine, which has become the focus of Russian military action following a withdrawal from areas close to the capital, Kyiv.

After Friday’s strike on a train station crowded with women, children and the elderly in the Donetsk region city of Kramatorsk, officials urged civilians in the neighbouring Luhansk region to flee.

“Yes, (Russian) forces are gathering in the east (of Ukraine),” Zelensky told a joint news conference with Austrian chancellor Karl Nehammer in Kyiv.

“This will be a hard battle, we believe in this fight and our victory. We are ready to simultaneously fight and look for diplomatic ways to put an end to this war,” Zelensky added.

Russia’s invasion, which began on February 24, has forced more than 4 million people to flee abroad, killed or injured thousands, left a quarter of the population homeless, and turned cities into rubble.

The civilian casualties have triggered a wave of international condemnation, in particular over the deaths in the town of Bucha, a town to the northwest of Kyiv that until last week was occupied by Russian forces.

Russia has denied targetting civilians in what it calls a “special operation” to demilitarise and “denazify” its southern neighbour. Ukraine and western nations have dismissed this as a baseless pretext for war.

Nehammer visited Ukraine a day after European Commission president Ursula von der Leyen — visits aimed at underlining the West’s support for Zelensky. In another such move, Italy said it would re-open its embassy in Kyiv after Easter.

Friday’s missile attack on the train station in Kramatorsk, a hub for civilians fleeing the east, left shreds of blood-stained clothes, toys and damaged luggage strewn across the station’s platform.

City mayor Oleksander Honcharenko, who estimated 4,000 people were gathered there at the time, said on Saturday that the death toll had risen to least 52.

Russia’s defence ministry denied responsibility, saying in a statement the missiles that struck the station were used only by Ukraine’s military.