Smoke billowed over the oil refinery outside the town of Lysychansk, amid the Russian invasion of Ukraine, on June 21, 2022. AFP
The Novoshakhtinsk refinery is located in Russia's Rostov region, a few kilometres from the border with Ukraine's separatist region of Lugansk.
"As a result of terrorist actions from the western border of the Rostov region, two unmanned aerial vehicles (UAVs) attacked the technical facilities" of the plant, the Novoshakhtinsk refinery said in a statement.
It added that as a result "an explosion occurred, starting a fire".
Rostov region governor Vasily Golubev said earlier that drone fragments were found at the site but did not specify where the drones may have originated.
Golubev said the fire had been put out and all plant staff have been evacuated with no casualties.
Work at the plant has been suspended pending an investigation, Golubev added.
Videos shared on social media -- which could not be independently verified -- showed drones flying over the plant shortly before an explosion took place.
Russia has several times accused Kyiv of launching attacks near the joint border since starting a military intervention in Ukraine in late February.
The fire at the refinery comes days after Moscow accused Ukraine of firing at Black Sea drilling rigs off the coast of Russia-annexed Crimea.