At least three people were injured in a Russian ballistic missile attack on the Ukrainian capital early Sunday morning, Ukraine's State Service for Emergencies said.

Several explosions were heard on Sunday morning in Kiev as Russia launched a fresh wave of air attacks on the city, triggering the operation of its air defense, according to Kiev's military administration.

The air attack has caused fires in the urban districts of Darnytskyi and Obolon, and rescuers are heading to the scene, said the Kiev military administration in a post on the social platform Telegram.

"Explosions in the capital. Air defense is in operation. Stay in shelters!" Mayor Vitali Klitschko was quoted as saying earlier on Telegram by media reports, adding: "The missile attack on Kiev is ongoing."

As of 7:16 a.m. local time (0416 GMT), 128 firefighters and 27 units of equipment were still working to deal with the aftermath of the strikes.