Russia has issued heavy penalties to those suspected of sabotage on Kyiv's orders in retaliation for Moscow's offensive in Ukraine, often by damaging railway infrastructure.

Maxim Bubenshchikov, 43, from Saint Petersburg was sentenced to 14-and-a-half years in prison after being found guilty of four acts of "sabotage" on railways and one attempted act after receiving instructions from an "unidentified person", the city's court press service said.

After buying tools at a hypermarket, Bubenshchikov set fire to relay equipment and filmed it on his phone, giving a pre-agreed crossed-finger hand signal to identify himself to his instructors, the court heard.

He received payment in cryptocurrency that was worth around $121, the court said.

The court said Bubenshchikov intended to "undermine the economic and defensive security of Russia".

Bubenshchikov denied he intended to commit sabotage.

He had previous convictions for vandalism and hooliganism and for painting advertisements for a drug dealer on fences, RAPSI court news agency reported.