A fire broke out at the terminal belonging to Novatek, Russia's largest liquefied natural gas producer, regional officials said on Sunday, amid reports of explosions and Ukrainian drone sightings in the area.

"According to preliminary information, the fire was the result of external influence," the company said in a statement, giving no further details.

"The technological process at Novatek-Ust-Luga has been stopped, and an operational headquarters has been established to eliminate the consequences. Damage assessment will be carried out later," the company said.

The Ust-Luga complex, located on the Gulf of Finland about 170 km (110 miles) west of St. Petersburg, processes stable gas condensate into light and heavy naphtha, jet fuel, fuel oil and gasoil, according to Novatek's website. The port is used to ship processed products to international markets.

(Writing by Maxim Rodionov; Editing by Andrew Osborn)