Kyiv has struck several Russian energy facilities throughout the nearly three-year conflict, claiming the hits were fair retaliation for Moscow's large-scale attacks on its own electricity grid.

Ukraine's General Staff said it had hit the Novoshakhtinsk oil refinery in Russia's southern Rostov region in an overnight attack.

The site is "used to meet the needs of the Russian armed forces," it said, adding: "A fire has been confirmed in the area of the facility."

The Russian governor of the Rostov region, Yuri Slyusar, had earlier reported a fire at the site after a "massive attack by the enemy, who used more than three dozen drones and three missiles."

The fire at the refinery -- which is 10 kilometres (six miles) from the international border with Ukraine, but 200 kilometres from the nearest Ukrainian positions (125 miles) -- lasted for more than six hours, according to posts on his Telegram channel.

Images shared on Russian social media showed a large bright fire raging at what was reported to be the facility, with thick grey smoke billowing into the air.

AFP could not verify the images.

A source in Ukraine's SBU security services told AFP that the combined missile and drone attack had caused "significant damage."

"SBU drones first overloaded the Russian air defences protecting the plant. By doing so, they created a window of opportunity for Ukrainian missiles, which the SBU and the Navy jointly used in the next stage," the source, speaking on condition of anonymity, said.

Russia's defence ministry said Ukraine fired a total of 84 drones towards its territory overnight. It said 36 were destroyed over the Rostov region, which borders Ukraine and is the military headquarters for Moscow's offensive.

Others were destroyed over the Bryansk, Belgorod, Voronezh, Kursk, Tambov and Krasnodar regions, the defence ministry said.

Russia's border regions are frequently targets by Ukrainian aerial attacks, and both sides have escalated their bombardments over the last few months.