By Lidia Kelly and Andrew Osborn
(Reuters) -Russia said on Monday it had shot down a Ukrainian drone close to one of its air bases for long-range bombers deep inside its own territory and that three Russian air force personnel had been killed in the incident.
The drone was allegedly flying near Russia's Engels air base where long-range strategic bombers that may have been used to target Ukrainian cities and infrastructure are based. No planes were damaged in the incident, the defence ministry said in a statement carried by Russian news agencies.
Unverified Russian and Ukrainian social media accounts reported that a number of planes had been destroyed however. Reuters was not able to independently verify those reports.
The air base, one of two strategic bomber bases housing Russia's air-delivered nuclear capability, is located near the city of Saratov, about 730 km (450 miles) southeast of Moscow and hundreds of kilometres from the frontlines in Ukraine.
There was no immediate comment from Ukraine, which has never publicly claimed responsibility for attacks inside Russia but calls them "karma" for Russia's Feb. 24 invasion.
The same base was attacked earlier this month by Ukrainian drones, Russia said at the time.
"A Ukrainian unmanned aerial vehicle (drone) was shot down at low altitude while approaching the Engels military airfield in the Saratov region," the defence ministry statement, published on Monday, said.
"Three Russian servicemen of the technical staff who were at the airfield were fatally wounded as a result of falling drone wreckage."
Russia has 60 to 70 strategic bomber planes of two types - the Tu-95MS Bear and the Tu-160 Blackjack. Both are capable of carrying nuclear bombs and nuclear-armed cruise missiles as well as conventional munitions.
Moscow has used its air force to fire cruise missiles in what it calls its "special military operation" to degrade Ukraine's military potential. Kyiv has said such attacks amount to war crimes and had likened Russia to a terrorist state.
The earlier Dec. 5 strike on the same base, along with another attack the same day on another base, raised questions about the effectiveness of Russian air defences and shocked Russian commentators.
If Ukraine could strike that far inside Russia, it may also be capable of hitting Moscow, they said on social media.
Earlier on Monday, Roman Busargin, governor of the Saratov region, said that civil infrastructure facilities had not been damaged in the latest incident at the base, which he said the authorities were investigating.
"There is absolutely no threat to residents ... Civil infrastructure facilities were not damaged," Busargin said.