Russia’s Slavneft Yaroslavnefteorgsintez (YANOS) oil refinery halted crude processing on Thursday after a Ukrainian drone attack damaged equipment at the facility, four industry sources told Reuters.

Yaroslavl Region Governor Mikhail Yevrayev said on Telegram that the region had repelled a major drone attack, The Caspian Post reports, citing Reuters.

“Sixty-five drones were downed. There were no casualties. The oil refinery sustained damage, and fires are being actively extinguished,” he wrote.

Ukrainian President Volodymyr Zelenskyy said Thursday that Ukraine had struck the Yaroslavl oil refinery overnight. The facility is located about 250 kilometers (155 miles) northeast of Moscow.

According to the sources, the attack damaged the refinery’s primary crude distillation unit, AVT-3, which has a capacity of 17,140 metric tons per day, accounting for approximately 40% of the plant’s total processing capacity.

The refinery has two other primary distillation units: AT-4, with a nominal capacity of 11,430 tons per day, or 27% of total capacity, and AVT-4, with a capacity of 14,300 tons per day, or 33% of total capacity.

The sources said the AVT-4 unit was already undergoing repairs after being damaged in an earlier drone attack on August 28.

Slavneft’s YANOS press service did not immediately respond to a Reuters request for comment.

Market participants said fuel produced by the Yaroslavl refinery was not offered for sale on the domestic commodity exchange on Thursday.

YANOS is owned by Slavneft, which is jointly controlled by Rosneft and Gazprom Neft. The refinery has an oil processing capacity of 300,000 barrels per day, or 15 million metric tons per year.

In 2024, the YANOS refinery processed 14.9 million tons of crude oil, producing 2.6 million tons of gasoline, 4.0 million tons of diesel, and 4.7 million tons of fuel oil, according to industry sources.