A Ukrainian drone attack on an airbase for bombers in southern Russia has left three people dead, Moscow says.
Air defences shot down the drone near the Engels base, but falling debris fatally wounded three technical staff, the defence ministry said.
Earlier this month, Russia accused Ukraine of a similar attack on the airfield, home to bombers that have carried out missile attacks on Ukraine.
The base lies about 500km (310 miles) north-east of Ukraine’s border.
The Ukrainian military has not officially admitted carrying out the latest attack, but air force spokesman Yuriy Ihnat said the explosions were the result of what Russia was doing on Ukrainian soil.
The latest incident will come as an embarrassment to Russian authorities, coming so soon after the two 5 December attacks hundreds of kilometres from the front line – both at the Engels base and in the Ryazan region.
Russia had also blamed falling debris for the deaths of three servicemen and what it described as light damage to two aircraft.
Social media early on Monday posted videos of blasts and air sirens in the vicinity of Engels airfield.
Russia’s defence ministry then said its air defences had shot down the drone flying at low altitude at about 01:35 on Monday (22:35 GMT Sunday).
Saratov governor Roman Busargin expressed his condolences to the men’s families and friends, and said there was “absolutely no threat to residents” in the town of Engels itself.
The Ukrainian air force spokesman said satellite imagery of the airfield would soon reveal the full damage from Monday’s attack, adding that earlier blasts had damaged aircraft at the base.
The Engels air base has been repeatedly used by Russia to carry out missile strikes on various targets in Ukraine since Moscow launched its full-scale invasion on 24 February.
The Kremlin has accused Ukraine of attacking its territory before, but the latest incidents have taken place far deeper in Russian territory.
After the 5 December attacks, there were widespread calls for tightened security around Russian military installations and the latest attack suggests that has not happened.