Russia’s fourth-largest oil refinery, the Ryazan plant located south east of Moscow, halted a primary crude distillation unit on October 23 following a Ukrainian drone attack, two industry sources told Reuters on Friday.

Ukraine has stepped up its attacks on Russia’s energy infrastructure as peace talks mediated by U.S. President Donald Trump have not progressed.

Such attacks have been behind motor fuel shortages across several regions in Russia, local authorities have said.

Ukraine’s general staff said on Thursday that Kyiv’s forces had struck the Ryazan oil refinery.

The industry sources in Russia told Reuters the CDU-4 processing unit, was urgently halted on Thursday after it caught fire following a drone attack.

The unit’s capacity stands at 4 million metric tons a year, or 80,000 barrels per day, accounting for around a quarter of plant’s total capacity.

Oil company Rosneft, which owns the refinery, did not respond to a request for comment. The sources said the plant is still processing oil, but at a reduced volume.

One of the sources said some adjacent units were also halted, including a reformer, vacuum gasoil hydrotreater and catalytic cracker.

The refinery processed 13.1 million tons of crude in 2024, producing 2.3 million tons of gasoline, 3.4 million tons of diesel and 4.2 million tons of fuel oil.