MOSCOW (AFP) - A Russian court on Tuesday found an activist guilty for his role in mass protests on the eve of President Vladimir Putin's inauguration last year and ruled that he must undergo treatment in a psychiatric hospital.

The court also found activist Mikahil Kosenko guilty of using violence against riot police but ruled that due to mental illness he was not responsible for his actions.

"The court ruled that Kosenko undergo compulsory medical treatment," his lawyer Valery Shukhardin told AFP, in a decision reminiscent of Soviet-era punitive psychiatry.

Kosenko has been diagnosed with a mild form of schizophrenia that is treated with medication.

He is one of a dozen activists accused of mass disorder when a peaceful opposition protest suddenly descended into violence on May 6 last year.

After the verdict was announced several dozen supporters rallying outside the Moscow court cried out "Shame" and "Freedom", an AFP correspondent said.