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

Russia's Investigations Committee formally brought charges against Leonid Razvozzhayev, a senior leader of the Just Russia party. A committee spokesman, Vladimir Markin, says Razvozzhayev turned himself in Sunday in Ukraine and admitted to involvement in organizing mass disturbances in Russia.

“Razvozzhayev explained in detail how, together with Sergei Udaltsov, Konstantin Lebedev and other people, they prepared the organization of mass disturbances on the territory of the Russian Federation. In that same document (confession), he reported that the same people were involved in the mass disturbances on Moscow's Bolotnaya Square on May 6. What is also important is he indicated that the funding was carried out by Givi Targamadze.”

But Razvozzhayev's supporters, among them opposition lawmaker Illya Ponomaryov, say he was kidnapped while in Ukraine, smuggled back into Russia and tortured into confessing.

“He (Leonid Razvozzhayev) was certainly kidnapped in violation of all international agreements and all international conventions. I have serious grounds to suspect that this so-called confession was obtained under torture.”

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.