Moscow's FSB security services accused Kyiv Friday of manipulating Russians to set fire to government buildings, warning that such "terrorist" acts had seen jail terms of up to 19 years being handed out.

Since Russia sent troops to Ukraine last year, there have been frequent reports of attacks on army enlistment offices and railway sabotage.

The FSB warned Kyiv was trying to "recruit" Russians online, offering "quick money" and "persuading (them) to commit arson of administrative buildings."

The powerful structure said sentences of "up to 19 years" had been handed out across Russia -- from the Moscow region to the Russian Far East -- and courts are examining 22 more cases.

"All criminals will receive well-deserved and strict punishment," it said, adding that Kyiv was targeting "young people, the elderly, radicals, marginalised people, as well as minors and persons with psychological illnesses" who were "not aware of the severity of the committed acts."

While there have been some instances of scammed pensioners in Russia, many Russians behind the arson attacks have said they acted to condemn the offensive in Ukraine and the Kremlin's mobilisation.

Thousands of Russians have been detained for protesting the military operation in Ukraine since the beginning of the conflict.