Russian investigators say they have charged an opposition activist with plotting riots based on evidence from a television documentary.

Russia's Investigations Committee formally brought charges against Leonid Razvozzhayev, a senior leader of the Just Russia party, who was arrested on Sunday in Kyiv, Ukraine. Prosecutors say Razvozzhayev turned himself in and admitted to involvement in organizing mass disturbances in Russia.

But his supporters say he was kidnapped while in Ukraine, smuggled back into Russia and tortured into confessing. Russia's Investigative Committee rejects the claims.

The Kyiv office of the U.N. refugee agency confirmed Monday that Razvozzhayev disappeared after registering with the agency last week.

Razvozzhayev was featured in a pro-Kremlin documentary in which he and other activists appeared to plan mass riots and a coup in an effort funded by a Georgian politician .

He faces up to 10 years if convicted, along with opposition activist Sergei Udaltsov and his aide, Konstantin Lebedev. Authorities launched a criminal probe against the two last week on charges they organized riots in May in Moscow.

Udaltsov was released and ordered to stay in Moscow, but Lebedev is in police custody.