UPDATE 5-Ukrainian drones strike Russian iron ore plant

(Adds Ukrainian claim of responsibility in paragraph 5, context)

MOSCOW, March 6 (Reuters) - Two Ukrainian drones struck fuel facilities at one of Russia's largest iron ore plants on Wednesday, though no one was injured and the plant was working as normal, Russian officials and the plant owner said.

Kursk governor Roman Starovoit said a second drone had hit the Mikhailovsky GOK iron ore plant which is owned by Metalloinvest, Russia's largest iron ore producer, around two hours after he announced a first strike.

He posted on social media that Russian air defences were in operation and urged people to remain calm.

Unverified video footage on Russian Telegram channels showed plumes of black smoke rising into the sky and damage at the plant, apparently after the first strike.

A source in Ukraine's GUR military intelligence agency told Reuters that it was responsible for the attack.

"Today, as a result of a drone attack in the Zheleznogorsky district, a fuel tank at the fuel and lubricants warehouse of the Mikhailovsky Mining and Processing Plant caught fire," Metalloinvest said in a statement after the first attack.

The company said in separate statements after both strikes that the plant was working as normal.

"There were no casualties. The necessary measures are currently being taken to extinguish the fire."

Starovoit had blamed Kyiv for the attacks on the plant in Kursk region's Zheleznogorsky district, which is known for its iron mines and is located around 90 km (56 miles) from the Ukrainian frontier. He said later that there was a risk of missile strikes on the area.

Mikhailovsky GOK is one of the largest iron ore mining and processing facilities in Russia. Through open-pit mining, Mikhailovsky GOK is developing an iron ore deposit with proven reserves of 10.4 billion tonnes, according to Metalloinvest.

Ukrainian drone attacks have repeatedly hit Russian oil refineries and other economic infrastructure in recent weeks. The Kursk region has come under regular attack in the course of the war.

The Mikhailovsky GOK previously came under attack in December, when Kursk governor Starovoit said that a Ukrainian drone had damaged a power line supplying part of the plant.

Ukraine has bet on long-range drones to strike targets deep inside Russia. Kyiv began the war without the long-range strike capabilities of its adversary, and its Western allies refused to provide long-range missiles for fear of escalating the conflict.

Russia carried out an overnight attack on Ukrainian regions on Wednesday with 42 drones, Ukrainian officials said. At least seven people were injured.

Separately on Wednesday, authorities in Russia's Belgorod and Voronezh regions, which are also regular targets for attack close to the frontline in Ukraine, said that drones had been downed there, too.

The Baza Telegram channel, which is close to Russian law enforcement, reported that the drones downed over Voronezh had been trying to attack a military airbase and an oil depot. (Reporting by Reuters; Writing by Felix Light in Tbilisi and Max Hunder in Kyiv; Editing by John Davison and Angus MacSwan)