A blaze at a natural gas terminal in the Baltic Sea port of Ust-Luga on Sunday was caused by an "external factor", said Novatek, Russia's biggest exporter of liquified natural gas.
The operator said there were no victims and the fire was "currently localised", at the site 110 kilometres (70 miles) west of St Petersburg near the Estonian border.
Neither Novaktek nor the authorities gave further details about the cause of the fire, which is 1,000 kilometres (600 miles) from the Ukrainian border.
Kyiv this week claimed responsibility for two attacks on oil depots in Russia, including one in the same Leningrad region where Ust-Luga is located.
The second attack in the Bransk region bordering Ukraine led to a major fire.
The Kremlin continues to present the conflict with Ukraine as having no effect on daily life in Russia.
But with Russia's presidential election approaching in March, Ukraine has stepped up drone and missile attacks over the border in enemy territory.
The authorities in Usk-Luga had offered a reassuring commentary on the gas terminal blaze, despite video posted on social media purporting to show columns of smoke and flames at the site.
"No casualties as a result of a fire at Novatek's terminal in the port of Ust-Luga. Personnel were evacuated," Aleksandr Drozdenko, governor of Leningrad Oblast, posted on Telegram along with a short video showing a massive fire and smoke at a chemical complex.
The Ria-Novosti news agency said a 100 cubic metre container was ablaze.
"A high alert regime has been introduced in the Kingiseppsky district (which includes the port)," Drozdenko said.
The Russian ministry of emergency situations and local fire service were involved in fighting the blaze, he added.
Local official Yuri Zapalatski said the fire started just before 2:45 am local time.
TASS news agency and other state media said the cause of the fire had not been announced.
Russia's defence ministry announced Sunday that Ukrainian attacks overnight had been foiled but made no mention of any incident in the Leningrad region.
The Ust-Luga complex processes natural gas condensate into naphtha, jet fuel and ship fuel components, according to Novatek's website.
The Nord Stream 2 gas pipeline leading to Germany, which has never entered into service after a sabotage raid in September 2022, starts from the town of Ust-Luga.
