The attack took place in Russia's Udmurt Republic, leaving 11 injured, three of whom were hospitalised, according to a Telegram post by Sergei Bagin, the local health minister.

“One of the republic's facilities was attacked by drones” launched by Ukraine, regional head Alexander Brechalov said in another Telegram post. He added that the strike caused injuries and damage but did not name the site or give further details.

An unofficial Russian news channel on Telegram, Astra, said Ukrainian drones struck the Votkinsk Machine Building Plant, a major state defence enterprise. Astra said its claim was based on an analysis of footage from local residents.

There was no immediate comment from Ukrainian authorities.

The Votkinsk factory, more than 1,400 kilometres from Ukraine, produces Iskander ballistic missiles, often used in strikes against the country, as well as nuclear-capable intercontinental ballistic missiles.

Other Russian news channels posted videos and photos, which they said were from Votkinsk residents, showing black smoke rising from an industrial site and blown-out windows on buildings.

Another unofficial Russian Telegram channel, SHOT, which often quotes contacts in the security services, said residents of Votkinsk reported hearing at least three blasts during the night, as well as what they thought was the humming of drones.