The Russian Defence Ministry on Monday said its air defences repelled dozens of Ukrainian drone attacks across a number of regions.
The Ministry said on the messaging service, Telegram, that a total of 80 drones were intercepted and destroyed in six regions.
Several explosions were heard in the Black Sea port city of Tuapse.
According to the Ministry, debris from an intercepted drone caused a large fire in an oil processing plant belonging to the energy giant Rosneft.
No injuries were reported, but Ukrainian media described the attack as a victory for Kiev’s military intelligence services, as the facility is important to the Russian war effort in Ukraine.
The plant, which includes a major oil terminal, has reportedly been the target of previous Ukrainian attacks.
Russian authorities said the fire has been extinguished.
A further 47 drone attacks were recorded in the southern Russian region of Rostov, while others were intercepted over the Crimean peninsula, which Moscow annexed in 2014.
Ukraine has been fending off the Russian invasion for more than two years.
It has repeatedly targeted military facilities on Russian territory, although the damage it has caused is seen as insignificant compared to the toll of Russian attacks in Ukraine attacks.