Ukrainian President Volodymyr Zelenskyy said he wants a tough global response to Russia after its forces fired a missile at a crowded train station, killing at least 52 people.

Zelenskyy’s voice rose in anger during his nightly address late Friday, when he said the strike on the Kramatorsk train station, where 4,000 people were trying to flee a looming Russian offensive in the east, amounted to another war crime.

Russia denied it was responsible for the strike. Among those killed were five children, and dozens of people were severely injured.

Photos taken after the attack showed corpses covered with tarpaulins, and the remnants of a rocket painted with the words “For the children” in Russian. The Russian phrasing seemed to suggest the missile was sent to avenge the loss or subjugation of children, although its exact meaning remained unclear.

The strike seemed to shock world leaders.

“There are almost no words for it,” European Union Commission President Ursula von der Leyen told reporters during a visit to Ukraine. “The cynical behavior (by Russia) has almost no benchmark anymore.”