At least 35 people were killed across Ukraine on Monday, as Russia launched a barrage of more than 40 missiles in a "massive" attack, Ukrainian officials said.

At least five cities fell under attack including the capital of Kyiv. Okhmatdyt Children's Hospital in Kyiv -- one of the most well-respected children's hospitals in the country -- was damaged, along with residential areas and other infrastructure, President Volodymyr Zelenskyy said on social media.

A massive Russian missile attack across Ukraine on Monday has left at least 31 dead and more than 150 injured, officials say, with one projectile slamming into a children’s hospital in Kyiv. 

Ukraine President Volodymyr Zelenskyy is now vowing to "hold Russia accountable for its acts of terror and Putin for ordering the strikes." 

In a series of messages posted on X, Zelenskyy said more than 40 types of missiles struck the cities of Kyiv, Dnipro, Kryvyi Rih, Slovyansk, and Kramatorsk, damaging apartment buildings and infrastructure as well. 

Nurse Olesia Filonenko was preparing for the first operation of the day at the Okhmatdyt children's hospital in Kyiv when she heard explosions "somewhere far away."

"Then, in a second, everything was blown away," she told the Kyiv Independent.

"Dust, smoke. We were all blown out of the operating rooms and into the corridors."

Russian forces had just launched a massive missile strike on cities across Ukraine, with Kyiv coming under particularly heavy attack.