Russian opposition leader Sergei Udaltsov, center, gestures as he is taken by police officers for questioning in Moscow, Wednesday (Photo: AP)
Russian investigators on Wednesday questioned Sergei Udaltsov, 35, the shaven-headed activist known for his punchy rhetoric and radical politics, after a pro-Kremlin national channel alleged in a documentary that he was plotting a violent uprising.
Udaltsov has dismissed the film aired 5 October as the "delirium of a lunatic".
Investigators announced on Wednesday evening that Udaltsov would not be detained on the charge of preparing mass riots but would need to sign a written undertaking not to travel, as he remained inside their Moscow headquarters.
"Sergei Udaltsov was questioned as a suspect," the investigative committee said, adding he was required to give a written pre-trial undertaking not to leave his place of residence and show good behaviour.
The statement from the top investigative body came after initial reports said Udaltsov had been detained for 48 hours for questioning.
Investigators said that another suspect, Udaltsov's aide Konstantin Lebedev, had been detained behind bars while they were seeking another suspect in the case who is an aide to a prominent opposition lawmaker.
Udaltsov was taken for questioning at the Investigative Committee's office after investigators searched his family apartment for more than five hours accompanied by masked Special Forces and removed several bags of evidence.
These are the most serious charges that the leader of the Left Front opposition movement has ever faced, even though he is often detained for public order offences at protests.
The probe was opened after a television film, "Anatomy of a Protest II," claimed Udaltsov was planning to overthrow the government with the help of foreign consultants and Chechen militants.
The film showed "facts of preparing for mass riots in Moscow and other regions of Russia," the Investigative Committee said in a statement.
It claimed Udaltsov was considering hiring Chechen militants to stage an uprising, and that he is bankrolled by former Bank of Moscow chief Andrei Borodin, currently in exile in Britain.
In the blurred hidden-camera footage, Udaltsov and his assistants purportedly meet Georgian lawmaker Givi Targamadze and plot a coup in Russia.
Investigators said there were "no signs of video montage in the materials" provided by NTV.
The agency has in the past come under fire for being overly politicised in its probes.
While Udaltsov has frequently urged protestors to hold peaceful sit-ins, he has denied calls for violent action and said last week the film appeared to be aimed at "preparing public opinion for new arrests."
"The case against Udaltsov is absolutely absurd. The fabrication is obvious, since it is based on nothing but edited film," anti-corruption crusader and fellow protest leader Alexei Navalny told the Moscow Echo radio station.
Udaltsov rose to prominence during the winter protests against Putin's 12-year political dominance, and has been one of the key speakers at opposition rallies.
Thirteen people are currently under arrest for alleged mass rioting during an opposition protest on 6 May, with four more barred from leaving Moscow during the investigation.
Putin returned to the Kremlin for a third term in May against the backdrop of an unprecedented wave of protests against his rule.
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