The Investigative Committee on Friday said it had charged Left Front leader Sergei Udaltsov with plotting riots, making him the second opposition leader to be implicated in a criminal case in recent months.

Udaltsov was charged at a scheduled meeting at the Investigative Committee office in Moscow on Friday. During questioning, Udaltsov did not admit his guilt and gave “detailed” testimony regarding the accusations, investigators said in a statement.

Before entering the Investigative Committee building, Udaltsov said he would not flee the country in the face of the charges.

“I'll hold out, I hope. Russia will be free,” he told journalists, Interfax reported. “If someone thought I would run across the border, he was mistaken.”

Udaltsov had already been named a suspect in the case, which stems from footage in an exposé aired on state-controlled NTV television earlier this month. His aide Konstantin Lebedev and fellow Left Front activist Leonid Razvozzhayev have been charged and detained as part of the same case.

Each of them faces up to a decade in prison if convicted on the charges of planning mass riots. Investigators did not arrest Udaltsov on Friday, saying he remained under travel restrictions that he had agreed to when called in for questioning in connection with the case on Oct. 16.

The circumstances surrounding Razvozzhayev's arrest have come under scrutiny by human rights groups and Western governments after he said he was abducted last week while seeking asylum in Ukraine and taken to Moscow by a group of unknown men before being handed over to investigators. He also said he was tortured.

While in custody, Razvozzhayev wrote a confession in which he implicated Udaltsov and Lebedev, according to investigators. He later recanted the statement, saying he had been pressured into writing it.

A State Department spokeswoman said Thursday that the United States was troubled by the case against the Left Front activists and against other opposition members, and that those concerns had been communicated to the Russian authorities.

“We are quite concerned about allegations that he [Razvozzhayev] was forced to confess, that he may have been subjected to torture, and we take concerns about this and other arrest actions taken against the May 6 protesters very seriously, including against Alexei Navalny, Sergei Udaltsov, Konstantin Lebedev and, now, Razvozzhayev,” spokeswoman Victoria Nuland said at a press briefing, according to a transcript posted on the State Department website.

“We continue to support the rights of all Russians to exercise freedom of expression and assembly regardless of their political views. And we have shared our concerns with the Russian government, including about the Razvozzhayev case,” she said.

In June, investigators searched the home of anti-corruption lawyer Navalny and those of Udaltsov and other prominent anti-Kremlin figures in connection with an inquiry into violence at a May 6 opposition rally on Bolotnaya Ploshchad.

Navalny was also charged on July 31 with stealing funds from state-owned timber company KirovLes during his time as an adviser to Kirov Governor Nikita Belykh in 2009.