Russian missiles and drones again crisscrossed Ukrainian skies on Monday night in strikes that killed more than 50 people and injured hundreds, Ukrainian officials said.

Most of the casualties were reported at an attack in Poltava, according to officials. Two ballistic missiles struck the Poltava Military Communications Institute as well as a nearby hospital, according to President Volodymyr Zelenskyy.

At least 51 people were killed and 217 injured in the attack in Poltava, according to Zelenskyy.

“I have ordered a full and prompt investigation into all the circumstances of what happened,” Zelenskyy said on his official Telegram channel on Tuesday morning.