KYIV, Oct 23 (AFP) - Pro-Russian authorities on Saturday (Oct 22) urged residents in the southern Kherson region, which Moscow claims to have annexed, to leave the main city "immediately" in the face of Kyiv's advancing counter-offensive.

It comes as President Volodymyr Zelenskyy said Russia launched 36 rockets overnight in a "massive attack" on Ukraine, following reported strikes on energy infrastructure that resulted in power outages across the country.

Kyiv's forces have been advancing along the west bank of the Dnieper river, towards the Kherson region's eponymous main city.

The first major city to fall to Moscow's troops, retaking it would be a key prize in Ukraine's counter-offensive.

In recent days, Russia has been moving residents in the region - which Moscow claims to have annexed in September - in efforts described as "deportations" by Kyiv.

"Due to the tense situation on the front, the increased danger of mass shelling of the city and the threat of terrorist attacks, all civilians must immediately leave the city and cross to the left bank of the Dnieper river," the region's pro-Russian authorities said on social media.

A Moscow-installed official in Kherson, Kirill Stremousov, told Russian news agency Interfax on Saturday that around 25,000 people had made the crossing.