A Russian airbase used to launch rocket attacks on Ukraine has been reportedly hit by a drone attack, causing a huge explosion and damage to two strategic bombers.

The TU-95 aircraft - known as Bears - form the backbone of Russia's long-range air attack nuclear forces. 

Video footage posted by an advisor to Ukraine's Minister of Internal Affairs shows a blast occurring at 6:04am at the Engels airbase, about 875km southeast of Moscow.

"Two TU-95 planes supposedly damaged after a reported drone attack on an air base in Russian Engels, Saratov region," said Anton Gerashchenko.

"Engels airbase is one of the take-off sites for Russian planes that launch rockets on Ukraine," he said.

News of the attack follows reports of a fuel tanker exploding at a Russian airfield near the city of Ryazan, killing three people and injuring six.

Ukraine has not claimed responsibility for either incident. 

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10 killed in Ukrainian attack on Alchevsk, reports Tass

Ten people have been killed after Ukraine shelled the Russian-held city of Alchevsk in Luhansk, the state-run Tass news agency reported.

The attack was carried out in the early hours of Monday morning using six Himars rockets and targeted refugees, according to local authorities.

"There are refugees among those killed. Those are the people who seem to have moved from the republic’s border cities and districts away from the line of fire, but the Kiev-regime’s military hit them with their Himars there," a law enforcement official said.

Luhansk fell under Russian control in early July after Moscow seized Lysychansk. Ukraine has since reclaimed some territory.