Pictures from the scene of the blast at the Kyiv hospital – which specialises in cancer treatment and organ transplants – showed children hooked up to IV drips sitting outside the damaged facility awaiting evacuation.
Rescue workers and medics dug through the rubble to look for survivors, though it was unclear how many were still trapped.
On Monday afternoon, Kyiv’s Mayor Vitali Klitschko said 16 people, including seven children, had been injured in the hospital strike.
He said the attacks across the city were among the worst Kyiv had faced since the beginning of the war, as he ordered flags to be flown at half-mast on Tuesday and cancelled entertainment events.
Following the strike, Ukrainian tennis player Elina Svitolina wore a black ribbon as a mark of respect when she played in the round of 16 at Wimbledon on Monday afternoon.