An industrial area near one of Russia's biggest oil refineries was damaged in a Ukrainian drone attack, a Russian official said on Thursday.

At least 40% of Russia's oil export capacity is at a halt following Ukrainian drone attacks, a disputed attack on a major pipeline and the seizure of tankers, Reuters reported on Wednesday.

More than 20 drones were shot down over the northern Leningrad region, according to Governor Alexander Drozdenko.

"The attack is being repelled over the Kirishi district. There is damage in the industrial area," Drozdenko said on Telegram.

Drozdenko did not specify what part of the industrial area was damaged, but the town of Kirishi is home to one of Russia's largest oil refineries, Surgutneftegaz's Kirishinefteorgsintez plant, which was repeatedly targeted by Ukraine last year.

According to industry sources, the refinery processed 17.5 million metric tons of oil (350,000 barrels per day) in 2024, which amounted to 6.6% of Russia's total oil refining volumes.

It produced 2 million tons of gasoline, 7.1 million tons of diesel, 6.1 million tons of fuel oil, and 600,000 tons of bitumen.

Russia's Baltic Sea ports of Primorsk and Ust-Luga, major exporting outlets, suspended crude oil and oil products loadings after Ukrainian drone attacks on Wednesday, two sources said.

Russian officials said earlier on Wednesday a fire broke out at Ust-Luga after a Ukrainian drone attack.