Russian forces have attacked several Ukrainian cities, killing at least four people in a drone strike on a residential area of Kyiv region.

Upper floors of two student dormitories were hit early on Wednesday in the city of Rzhyshchiv, on the outskirts of the capital. 

An 11-year-old was among the wounded, rescue services said.

Separately, officials in Russian-annexed Crimea said a Ukrainian drone attack on their fleet were repulsed.

Explosions were reported by residents in the port city of Sevastopol.

The head of Russia's occupation authority Mikhail Razvozhaev said three "objects" targeting the Black Sea Fleet had been destroyed and Russian warships were not damaged. 

There was no comment from Ukraine's military, which said earlier this week it had destroyed missiles destined for the fleet at a rail hub in Dzhankoi in northern Crimea.

Ukrainian President Volodymyr Zelensky said Russia had launched more than 20 "killer drones", as well as missiles and shells. 

Referring to Chinese President Xi Jinping's departure from Russia hours earlier, he said that every time "someone tries to hear the word 'peace' in Moscow", another order was given to launch attacks.