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

The air attack has caused fires in the urban districts of Darnytskyi and Obolon, and rescuers are heading to the scene, said the Kyiv 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 Kyiv is ongoing."