The apparent attack came a day after a Ukrainian strike killed four people in a Russian village in the Bryansk region and as Kyiv prepared for a widely expected counter-offensive.
"An unidentified explosive device went off, as a result of which a locomotive of a freight train derailed," Bryansk governor Alexander Bogomaz said on Telegram, according to Moscow Times.
There were no casualties, he added.
Bogomaz said the device went off "on the 136th kilometer" of the railroad between regional hub Bryansk and the town of Unecha, towards the border with Ukraine.
He said emergency services were working at the scene and that rail traffic in the area had been suspended.
There have been reports of sabotage acts on railroads in Russia and its ally Belarus throughout Moscow's more than year-long Ukraine offensive.
Also on Monday, the governor of the northern Leningrad region, Alexander Drozdenko, said local power lines had been blown up by an "explosive device."
Drozdenko later said the FSB security service had opened a criminal case on "sabotage."
MNA/PR