A missile hit a train station in eastern Ukraine where thousands had gathered Friday, killing at least 52 and wounding dozens more in an attack on a crowd of mostly women and children trying to flee a new, looming Russian offensive, Ukrainian authorities said.

The attack that some denounced as yet another war crime in the 6-week-old conflict came as workers unearthed bodies from a mass grave in Bucha, a town near Ukraine’s capital where dozens of killings have been documented after a Russian pullout.

Photos from the station in Kramatorsk showed the dead covered with tarps, and the remnants of a rocket with the words “For the children” painted on it in Russian. About 4,000 civilians had been in and around the station, heeding calls to leave before fighting intensifies in the Donbas region, the office of Ukraine’s prosecutor-general said.

Ukrainian President Volodymyr Zelenskyy, who says he expects a tough global response, and other leaders accused Russia’s military of deliberately attacking the station. Russia, in turn, blamed Ukraine, saying it doesn’t use the kind of missile that hit the station — contention experts dismissed.