In a business he conducted the Security Service of Ukraine (SBU) attributed to the fire that broke out last night in a Siberian railway tunnel used to resupply Russian troops, according to a Ukrainian source cited by the Reuters news agency.

Four explosive devices were detonated in the Severomuisky railway tunnel in the republic of Buryatia, near the border with Mongolia, the official said, speaking on condition of anonymity. If confirmed to be Ukrainian sabotage, it would be an impressive demonstration of Kiev’s ability to strike targets deep inside Russian territory. The aforementioned rail tunnel is more than 4,000 kilometers from the Ukrainian border.

Russian media reported that a train passing through the scene was engulfed in flames, without any mention of explosives.

The state-owned company that runs the rail network said the train was stopped after smoke was seen coming from a diesel fuel tank.

The Investigative Committee of the Russian Federation said in a statement that a train carrying fuel burst into flames inside the railway tunnel on Wednesday night, with no casualties. The causes of the fire are being investigated, the announcement emphasizes.