The incident is the latest in a series of explosions on Russian territory.
The local governor, Roman Starovoyt, has claimed that there is a possibility of subversive activity behind Sunday's railway bridge collapse in Russia's Kursk Region. The area borders Ukraine.
There have been no reports of casualties linked to the incident, but it disrupted a railway line linking two Russian towns near the frontier.
The Russian Investigative Committee launched a probe into the suspected act of terrorism after authorities said the bridge was apparently damaged by an explosion.
The information has been confirmed. Starovoyt said in a video address published on Telegram that it was an act of sabotage and promised to provide further details at a later date.
Russian investigators and security services are currently working to determine the identities of those involved, as well as the power and type of explosive device used.
The bridge connected the town of Sudzha, about 10 km from Ukraine, with Sosnovy Bor. The governor told Russian media that it was part of a line mostly used by freight trains.
Starovoyt previously accused Kiev's forces of shelling border crossings in his region on April 29 and 30. There were no casualties in the incidents.
On Sunday, the head of Russia's Belgorod Region, located southeast of Kursk and bordering Ukraine s Kharkov, reported a fire at a military site not far from the frontier. The Russian Defense Ministry has yet to make a statement on the matter, and details of the incident are still unclear.
Kiev has not claimed responsibility for any of the incidents on Russian territory.
Russia attacked Ukraine after Kiev failed to implement the terms of the Minsk agreements, first signed in 2014, and Moscow s eventual recognition of the Donbass republics of Donetsk and Lugansk. The German and French protocols were designed to give the breakaway regions special status within the Ukrainian state.
The Kremlin has demanded that Ukraine officially declare itself a neutral country that will never join the US-led NATO military bloc. Kiev insists that the Russian offensive was unprovoked and has denied it plans to retake the two republics by force.