Russia's Leningrad region, home to a fuel export terminal disrupted on Sunday by a fire that Ukrainian media reported was the result of a Ukrainian drone attack, announced it had put key facilities on high alert.

"In all districts of the Leningrad region, a high alert regime has been declared at critical infrastructure facilities," the regional administration said on Telegram.

"Security units and law enforcement agencies have received orders to destroy Unmanned Aerial Vehicles if they are detected in nearby territories," it said.

The Interfax-Ukraine news agency, citing unnamed sources, said the fire at the Ust-Luga complex, on the Gulf of Finland about 110 miles west of St. Petersburg, was the result of a special operation carried out by Ukraine's security services.