A Russian attack involving nearly 500 drones hit Ukraine's energy infrastructure, killing two people and prompting power cuts in several regions, Ukrainian authorities said on Saturday.

Moscow has in recent months escalated strikes on energy infrastructure in Ukraine, damaging natural gas facilities which produce the main fuel for heating in the country.

The Ukrainian air force said Russia had launched 458 drones and 45 missiles overnight, adding that it had downed 406 drones and nine missiles.

Moscow's Defence Ministry said it had launched "a massive strike with high-precision long-range air, ground and sea-based weapons" in response to Kyiv's strikes on Russia.

It added that it had struck "enterprises of the Ukrainian military-industrial complex and gas and energy facilities that support their operation."

'Technological disaster'

The attacks on energy infrastructure have raised concerns of heating outages in Ukraine as the conflict enters its fourth winter.

Ukraine's top energy expert said on Wednesday that if Kyiv's two power and heating plants went offline for more than three days when temperatures fall below minus 10 degrees Celsius, the capital would face a "technological disaster".

Ukraine has in turn stepped up its attacks on Russian oil depots and refineries in recent months, seeking to cut off Moscow's vital energy exports and trigger fuel shortages across the country.

On Friday evening, drone attacks on energy infrastructure in southern Russia's Volgograd region caused power cuts there too.

Governor Andrei Botcharov said Russian forces repelled a "massive" night time strike on energy facilities in the southern Volgograd region, with power in some parts knocked out. 

Russia's Defense Ministry said its forces shot down 82 Ukrainian drones during the night and two people were injured in the neighboring Saratov region after a drone strike blew out windows in an apartment block.

On the ground, Moscow said its forces continued to advance in grinding battles around the key towns of Pokrovsk and Kupiansk, and had captured a tiny village in eastern Ukraine.

An aide to the head of the Donetsk People's Republic warned Ukrainian troops in Pokrovsk they had "lost their last opportunity" to withdraw after Russian military had blocked all routes out of the city.

"The enemy can no longer leave (Pokrovsk). The last route is now completely under our control," Igor Kimakovsky said.