(Reuters) -Russia launched a third nightly round of attacks on Kyiv in six days, authorities in the Ukrainian capital said on Wednesday, with a drone hitting a building in the Dnipropetrovsk region as Moscow steps up attacks on its neighbour.

Ukraine's Air Force Command said its forces destroyed 21 of the 26 Iranian-made Shahed drones launched by Russia, while Kyiv officials said air defence systems eliminated those sent over the city, with no initial reports of casualties or destruction.

"All enemy targets were identified and shot down in the airspace around the capital," Kyiv's military administration said on the Telegram messaging app, citing initial details.

Air raid sirens blared for several hours in Kyiv, the surrounding region and most of eastern Ukraine, with the skies only clearing towards dawn.

Russia has intensified attacks on Ukraine ahead of a counteroffensive widely expected by the latter, sending nearly nightly waves of drones and missiles to target Kyiv and other areas over the past week.

One of Wednesday's drones hit an administrative building in Dnipro, the administrative centre of the Dnipropetrovsk region, its governor, Serhiy Lisak, said on Telegram, and set it on fire, although that was put out by morning.

Air defence units shot down seven drones over the region, he added.

(Reporting by Lidia Kelly in Melbourne; Editing by Clarence Fernandez)