At least 50 people were killed on Friday after a missile hit a train station where thousands of people had gathered to flee in eastern Ukraine, authorities said. Officials said many of the wounded had lost limbs and were being operated on after the strike in the city of Kramatorsk, which President Volodymr Zelenskyy said was a deliberate attack on civilians using a Tochka U short-range ballistic missile.

Photos from the station showed the dead covered with tarps on the ground and the remnants of a rocket with the words “For the children” painted on it in Russian. About 4,000 civilians were in and around the station at the time of the strike, the office of Ukraine’s prosecutor-general said, adding that most were women and children heeding calls to leave the area before Russia launches a full-scale offensive in the country’s east.

“Lacking the strength and courage to stand up to us on the battlefield, they are cynically destroying the civilian population,” Zelenskyy said in a statement. “This is an evil that has no limits. And if it is not punished, it will never stop.”

The killings were revealed after Russian forces pulled back from the Ukrainian capital of Kyiv after failing to take the city in the face of stiff Ukrainian resistance. Russian troops are now regrouping and have set their sights on the Donbas, a mostly Russian-speaking, industrial region in eastern Ukraine where Moscow-backed rebels have been fighting Ukrainian forces for eight years and control some areas.

The train station hit in Friday’s missile strike is located in government-controlled territory, but Russia insisted it wasn’t behind the attack. Moscow-backed separatists, who also operate in the region and work closely with Russian regular troops, also blamed Ukraine for the strike.

Kremlin spokesman Dmitry Peskov said the country’s forces “do not use” the type of missile that hit the station.

Military experts dismissed that, saying Russia has already used the same type of missile during the war and has the only logical motive for attacking a rail station at this stage of the war.

Ukrainian officials have pleaded with Western powers to send more arms and further punish Russia with sanctions to stop the offensive. NATO nations agreed Thursday to increase their supply of arms.