It came the day after two explosions rocked a pair of air bases even further inside Russian territory, which killed three military personnel in the Ryazan region, and Russian Engels-1 airbase in Saratov. Those incidents were also subsequently described by the defense ministry as the result of drone attacks.

The Russian city of Kursk, which lies closer to Ukraine than the other two sites of attack, had thick black smoke rising over its airfield in the early Tuesday hours. "Oil tankers at a base near the city of Kursk, around 60 miles from the border, were on fire and streaming smoke into the sky early Tuesday morning," The Daily Mail writes based on regional sources.

International reports say the large Kursk fire has burned for some ten hours, given a large oil depot was ignited, following the attack:

The inferno covered almost 5,500 square feet and new teams of firefighters were being rushed to the scene, local media said.

Suspected Ukrainian drones also attacked the Belbek military airport in Sevastopol - but were downed by air defenses, say reports.