Russia was hit by two separate May Day “saboteur” explosions which led to an oil train igniting in flames after derailing and electricity pylons collapsing.
The rail incident was in the Bryansk region, bordering Ukraine and Belarus on a rail route used for Moscow’s military supplies.
Seven oil tanker wagons came off the track and overturned after an explosion on the rail track, said reports.
Regional governor Alexander Bogomaz: "An unidentified explosive device went off in the Unechsky district….on the Bryansk-Unecha railway.
“The locomotive of a freight train derailed. There were no casualties. Traffic on this section of the railway was suspended.”
A Russian Railways source said: "As a result of the incident, the locomotive caught fire.”
In a separate incident, power cables were brought down by explosives on pylons close to Russia ’s second city St Petersburg.
A blast moments after midnight caused the collapse of the main power lines and evidence of an explosive device was found at dawn, say law enforcement.
Officials said the St Petersburg attack was sabotage and the incidents in Russia are seen as linked to Vladimir Putin ’s war against Ukraine.
There has been an upsurge in explosions and fires in Russia in recent months.
The latest incidents come as Ukraine is expected to stage a counteroffensive against Putin’s forces.
Ukraine’s intelligence chief Major-General Kyrylo Budanov said that some incidents in Russia are orchestrated by Ukraine.
“Much of this is no accident,” he said.
“Something is constantly on fire [in Russia]. Signalling equipment on railways lights up several times a day, on various highways constantly for two to three hours, sometimes for five to six hours, traffic gets suspended.
“Clearly it doesn’t just happen like this…. I would put it this way: money works wonders.”
Two alleged saboteurs behind the Bryansk railway explosions were spotted on security cameras, reported Russian news outlet Mash.
They are being sought by police and security services.
A new video shows the fire damage to two derailed locomotives pulling the train.
“This is how the fire extinguishing is going on,” said TV pro-war reporter Sergey Karnaukhov.