A Ukrainian drone attack on Engels bomber base in south Russia has left three people dead, Moscow says. 

Air defences reportedly shot down the drone but falling debris caused the casualties in the overnight attack. 

Russia accuses Ukraine of carrying out a similar attack on the airfield, home to strategic bombers, on 5 December. The base lies about 500km (310 miles) north-east of the border with Ukraine.

The Ukrainian military has not officially commented on those attacks.

Russia's defence ministry says its air defences shot down the Ukrainian drone flying at low altitude at about 01:35 local time on Monday (22:35 GMT Sunday).

Three Russian servicemen died of injuries caused by drone debris, it adds.

Earlier, social media users posted videos where what sound like blasts and air sirens can be heard at the Engels airfield.

The governor of Saratov region said there was "no threat to residents" of the town of Engels itself.

In the previous reported attack on 5 December on the airfield and another air base in the Ryazan region, three servicemen were also killed by debris from a downed Ukrainian drone, Moscow said at the time. Two aircraft were lightly damaged.

The Ukrainian military made no comment on the reported attacks. 

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 alleged attacks in December are deeper into Russia than previous ones. 

A number of military experts in Ukraine and the West have described the reported strikes as embarrassing for the Russian military.