Ukrainian long-range attack drones struck four Russian oil refineries as well as radar stations and other military targets in Russia in a major attack in the early hours of Friday, Kyiv's military said.

Ukraine has dramatically stepped up its use of drones this year to attack Russian oil facilities, which it deems legitimate military targets that are fuelling Russian troops in their nearly 28-month-old invasion.

"Unmanned aerial vehicles attacked the Afipsky, Ilsky, Krasnodar, and Astrakhan oil refineries," the Ukrainian military said in a statement on the Telegram messaging app.

Russia's military said earlier that it had downed 70 drones over the Black Sea and Ukraine's occupied Crimean peninsula, 43 drones over Russia's Krasnodar region and one more over Russia's Volgograd region on Friday.

A Kyiv intelligence source told Reuters that the Afipsky, Ilsky and Krasnodar oil refineries produced fuel for Russia's Black Sea Fleet and that the drone operation targeting them had been conducted jointly with the SBU security service.

"The damage of these refineries will significantly complicate the logistics of fuel oil supply, making it more expensive and time-consuming, as it will have to be delivered from other refineries," the source said.

The Ukrainian military said it also targeted radar stations and electronic intelligence centres in the Bryansk region and occupied Crimea. The statement did not say exactly what those sites were.

Drone storage and launch sites, command and control centres in Russia's Krasnodar region were also struck, it said, adding they had confirmed explosions and fires at these facilities.

The source said the drone attack had targeted a training centre in the town of Yeisk in Krasnodar region used by Russia to launch drone attacks against Ukraine.

The Ukranian military, in their statement, also claimed responsibility for Thursday's drone attacks carried out on fuel depots in the Russian regions of Tambov and Adygeya.

Friday's drone attack came after Russia conducted the latest in a series of air strikes on Ukrainian power facilities that have caused blackouts and raised fears about how the grid will hold up this winter.

The Russian strikes on the power grid have dealt significant damage to Ukraine's energy generating capacity since March. Moscow said that some of the strikes were retaliation for Ukrainian attacks on Russian territory. (Reporting by Anastasiia Malenko and Tom Balmforth; Editing by Alison Williams and Christina Fincher)