ST PETERSBURG — An explosion has occurred at a gas export terminal near the city of St. Petersburg in Russia, officials say.

The blast caused a large fire, state-owned Ria Novosti news agency said. It said the fire had been contained, and there were no reports of injuries.

The cause of the fire is not known, but local media have reported that drones had been seen in the area.

Ukraine usually does not admit such attacks. But Ukrainian media cited sources saying Kyiv was behind it.

Both Russia and Ukraine have used drones in the current conflict.

Russia launched its full-scale of invasion of Ukraine nearly two years ago, but has made little progress in recent months.

On Sunday, 25 people were killed and 20 injured by shelling in the Russian-controlled city of Donetsk in eastern Ukraine, Alexei Kulemzin, the city's Russian-installed mayor said. Kyiv has also not commented on that attack.

Regarding Sunday's explosion near St. Petersburg, regional governor Alexander Drozdenko said a "high alert regime" was in place after the incident at the terminal of gas producer Novatek, in Ust-Luga on the Gulf of Finland. He shared a video of what appeared to be a large fire.

Novatek later announced that work at the terminal had been suspended, and said the fire was the result of "external influence", without providing further details.

Russian news outlet Shot quoted local residents as saying they heard a drone followed by several explosions at Ust-Luga, close to Russia's border with Estonia.

Fontanka, a St Petersburg-based news outlet, said at least two drones were spotted flying towards the city before the fire broke out.

It said there were three large international tankers near the fire, although there were no reports of damage to them.

The BBC has not verified the details of what happened, and there has been no comment from Ukrainian officials.

Russia's Defense Ministry also said it shot down three Ukrainian drones in Smolensk Region, close to its border with Ukraine, on Saturday night.

It earlier said it had shot down drones over Tula and Oryol, both in western Russia. There were no reports of casualties.

Russia and Ukraine have been targeting each other's energy infrastructure, and on Friday a fire broke out at an oil depot in Bryansk, southwest Russia, which Moscow blamed on a Ukrainian drone strike.

That came a day after an attack targeted a major oil loading terminal in St. Petersburg.

On Thursday, Russia claimed to have captured a village close to the devastated city of Bakhmut, in Ukraine's eastern Donetsk region. Kyiv has not confirmed the claim.

Ukraine has warned repeatedly that its army is facing severe ammunition shortages, but has set a target of producing a million drones domestically this year.

Russia launched the invasion of its neighbor nearly two years ago. — BBC