Three Russian military personnel were killed early on Monday by falling wreckage of a Ukrainian drone that was shot down as it was attacking a base in Russia’s Saratov region, Russian news agencies reported, citing the defence ministry.

It was the second attack on the base this month.

“A Ukrainian unmanned aerial vehicle was shot down at low altitude while approaching the Engels military airfield in the Saratov region,” news agencies reported the Russian ministry as saying.

“As a result of the fall of the wreckage of the drone, three Russian servicemen of the technical staff who were at the airfield were fatally wounded.”

The base, near the city of Saratov, about 730 km (450 miles) southeast of Moscow and hundreds of kilometres from the front lines in Ukraine, was hit on Dec. 5 in what Russia said was Ukrainian drone attacks on two Russian air bases that day.

The twin strikes dealt Russia a major reputational blow and raised questions about why its defences failed, analysts said, as attention turned to the use of drones in the war between neighbours.

Ukraine has never publicly claimed responsibility for attacks in Russia, but has said, however, that such incidents are “karma” for Russia’s invasion.

The Russian defence ministry said that aviation equipment was not damaged but according to unofficial Russian and Ukrainian social media reports a number of planes was destroyed.

Reuters was not able to independently verify the reports.

Earlier on Monday, Roman Busargin, the governor of the Saratov region, said that civil infrastructure facilities were not damaged in the incident.

“There is absolutely no threat to residents … Civil infrastructure facilities were not damaged,” Busargin said.