Russian President Vladimir Putin has ordered the Prosecutor General to investigate if a guilty verdict for Moscow protester Konstantin Kotov was lawful, the Kremlin said.

A Moscow court sentenced Kotov, a 34-year-old programmer, to four years in prison in September for "repeated" participation in unauthorized rallies, under a widely criticized law that has made non-violent protests a criminal offense.

The court said Kotov "disregarded basic constitutional principles" because he continued to take part in unauthorized protests after being found guilty of violating legislation on public gatherings.

Putin ordered an investigation into Kotov's conviction to establish if the verdict was lawful and justified, the Kremlin said on its website.