Russia's military said early on Monday that air defence units had downed 148 Ukrainian drones over a three-hour period and officials said emergency crews were restoring power to nearly half a million households in outages linked to air attacks.

On Sunday evening, a drone killed a civil defence volunteer in Russia's border region of Belgorod, a frequent target of the Ukrainian military, and drones also hit an apartment building in Russia's Black Sea port of Novorossiysk.

A Russian Defence Ministry statement said air defence units had intercepted 148 drones, mostly in central and southern areas of the country, between 8 p.m. and 11 p.m. (1700-2000 GMT) on Sundasy.

The mayor of the port of Novorossiysk, Andrei Kravchenko, said drone debris had struck a high-rise apartment building. There was no word on casualties.

In Crimea, a region seized and annexed by Russia in 2014, 10 years before the full-scale invasion, the governor of the port of Sevastopol said his city had come under four drone attacks throughout the day. Seven drones were downed in the latest wave.

In Russian-occupied Donetsk region in eastern Ukraine, the head of the Russia-installed government, Andrei Chertkov, said repair crews had restored power to two major cities, Donetsk and Makiivka, after Ukrainian attacks on energy infrastructure.

Chertkov had earlier said that nearly half a million households had been left without electricity. Work was continuing in areas still without power.

Crews were also restoring power after mass outages in Russian-held areas of Zaporizhzhia region.