Ukrainian authorities issued an alert for a missile attack on Kyiv early Thursday, with AFP journalists reporting explosions heard across the capital.

"Kyiv is being attacked by enemy missiles," the city's military authorities said in a post on Telegram.

They reported damage in at least two districts and urged residents to take shelter. Flights of drones were also heard over the city.

In a bomb shelter set up in the basement of a residential building, over a dozen residents gathered after the air alert was issued, according to an AFP journalist.

Kyiv Mayor Vitali Klitschko said a three-year-old child had been taken to the hospital, later confirming that at least 21 people were injured.

"The 21st casualty was already hospitalised," Klitschko said.

Kyiv was last struck by missiles on 5 April, when at least three people were wounded. The capital has been the target of sporadic attacks since Russia launched its full-scale invasion in February 2022.

In eastern Ukraine, the city of Kharkiv was hit by seven missiles, according to Mayor Igor Terekhov.

Andriy Yermak, a top aide to Ukrainian President Volodymyr Zelensky, said Russia was attacking Kyiv, Kharkiv, and other cities "with missiles and drones right now."

"Putin shows only a desire to kill," he said. "The attacks on civilians must stop."