MOSCOW (AP) — A drone strike caused a fire at a refinery in southwestern Russia near the border with Ukraine on Wednesday, but no one was hurt and the blaze was contained quickly, officials said.

The fire engulfed industrial equipment at the Novoshakhtinsk oil processing plant in the Rostov-on-Don region. The authorities said that dozens of firefighters extinguished the flames in a half-hour and no one was hurt.

The refinery said in a statement that the fire was caused by a strike carried out by two drones, describing it as a "terrorist" act. It didn't give further details, but the state news agency Tass said that two Ukrainian drones flew over the plant and one of them slammed into a heat exchanger, triggering the fire.

Ukrainian officials haven't claimed responsibility for the drone strike.

A video posted on a messaging app channel showed a drone flying by and hitting what was purported to be the refinery, a giant plume of smoke rising into the sky. The authenticity of the video couldn't be independently verified.

The Rostov regional governor, Vasily Golubev, said that fragments of two drones were found on the territory of the plant.

The refinery said it temporarily suspended the operations to assess the damage.

Wednesday's attack on the refinery follows a series of explosions and fires in western Russia amid Moscow's fighting in Ukraine in an operation that began nearly four months ago.

In April, two Ukrainian helicopter gunships struck an oil depot in Belgorod, according to Russian officials, causing a massive fire.

Several other explosions and fires hit refineries, oil depots, and an ammunition storage facility. Ukraine hasn't officially taken responsibility for the incidents, but some Ukrainian media have lauded them as a result of Ukrainian strikes.