The man, from Zheleznogorsk in the Krasnoyarsk region, was accused of having "deliberately and intentionally" defaced 13 recruitment posters last June.

A court found him guilty of having "discredited" Russian forces, the authorities said. The charge has been used to suppress dissent to the conflict in Ukraine.

Russia has cracked down hard on opposition to the conflict, which began in February 2022, and has sanctioned, threatened or imprisoned thousands.

The number of arrests on suspicion of espionage, treason, sabotage, extremism and even "discrediting the army" have increased, often with heavy prison sentences.

In many cities and regions, public poster campaigns emphasise increasing amounts of money for those willing to fight in Ukraine, as the third anniversary of fighting approaches.