Two industrial sites in Russia’s republic of Tatarstan, around 1,100 kilometers from the Russian-Ukrainian border, were hit in a drone attack on Tuesday morning, officials said.

A defense source in Kyiv told AFP that Ukraine’s GUR military intelligence agency was behind the strikes, which it said hit facilities where Iranian-designed Shahed drones are assembled.

The source did not say where the attack was launched from, though if launched from Ukrainian-held territory, it would be one of the most far-reaching drone strikes carried out by Ukrainian forces since Russia’s full-scale invasion over two years ago.

“Facilities in Yelabuga and Nizhnekamsk were attacked by unmanned aerial vehicles,” Tatarstan’s leader Rustam Minnikhanov said in a post on the messaging app Telegram.

At least six people were injured in the attack in Yelabuga, the state-run TASS news agency reported, citing local emergency services.

Videos on social media showed an aircraft-style drone flying into a two-story building at a business park outside the city before exploding, sending a fireball into the air.

Minnikhanov said there was no serious damage and production at the facility continued.

The mayor of Nizhnekamsk said air defense systems had thwarted an attempted attack on an oil refinery, TASS reported. He said there was no damage or injuries.

The RIA Novosti agency said a drone hit the site of the Taneco oil refinery, which is owned by the oil and gas company Tatneft.

Citing emergency services, the news agency reported that a resulting fire was put out within 20 minutes and production continued uninterrupted.

Ukraine has claimed responsibility for several drone strikes on oil refineries deep inside Russian territory, arguing that they are a legitimate retaliation to Moscow’s targeting of its energy facilities and aim to cripple Russia’s fuel sector, vital for both its military and export earnings.