Russian air defences thwarted a drone attack on Monday on the Slavneft-YANOS oil refinery in the city of Yaroslavl, northeast of Moscow, regional governor Mikhail Yevrayev said.
He said there was no fire and no casualties at the plant, located some 250 kilometres (155 miles) from Moscow.
"Law enforcement agencies and special services are working at the scene. There were no injuries, no fire," the governor wrote about the incident at the oil refinery, Russia's third-largest by output in 2022.
The attempted attack followed a series of similar drone raids on Russian energy infrastructure in recent weeks, some of which have disrupted fuel production.
A source, familiar with the situation, said the drone fell at around 0700 (0400 GMT). It had not affected fuel output, while fuel supplies were briefly interrupted but soon resumed.
The plant's annual capacity stands at 15 million metric tons (300,000 barrels per day).
