MOSCOW, May 20 (Reuters) - Russia's Lukoil last week restarted a key production unit at its Volgograd refinery, the largest in southern Russia, which was shut earlier this month after being damaged in a drone attack, two industry sources told Reuters on Monday.

The plant, with production capacity of some 300,000 barrels per day (bpd), caught fire on May 12 following a drone strike, local officials said. Sources said the CDU-1 unit had been damaged in the attack.

Lukoil did not immediately reply to a request for comment.

Ukraine does not officially confirm or deny attacks on oil refineries inside Russia, but it says the facilities are legitimate targets helping the Russian war effort at a time when Russian strikes are pounding Ukrainian energy infrastructure.

The Volgograd refinery was also attacked by drones in February and was able to conduct maintenance within 18 days.

The CDU-1 unit has a capacity of 18,590 metric tons per day, and annual production of 6.5 million metric tons, or 130,000 bpd, of oil.

It makes up 43% of the refinery's capacity and accounted for 49% of actual refinery processing in the first quarter of 2024. (Reporting by Reuters; Writing by Vladimir Soldatkin; Editing by Jan Harvey)