Richard Sobolev, one of the two released suspects, is believed to have been a member of a neo-Nazi group that participated in attacks on migrant workers.
Investigators have released two people believed to have taken part in clashes with riot police at a May 6 opposition rally, a move that comes shortly after President Vladimir Putin said their detention should be reviewed.
Ilya Arkhipenkov, 27, and Richard Sobolev, 22, have been released after two months in pretrial detention on the condition that they do not leave Moscow, Investigative Committee spokesman Vladimir Markin said Friday.
The pair was released because the main investigation into their actions has been completed and they both live in Moscow, Markin said, Itar-Tass reported.
Arkhipenkov and Sobolev are accused of taking part in clashes with riot police at a sanctioned "March of Millions" opposition rally on Bolotnaya Ploshchad on May 6, a day before Putin took office for his third term as president.
The pair's defense team said Friday that they were able to convince investigators that their clients have alibis and were not on Bolotnaya on May 6.
The decision by investigators to free Arkhipenkov and Sobolev comes soon after attendees of the pro-Kremlin Seliger summer camp complained to Putin that the two defendants were wrongly accused.
"Let's check it one more time," Putin responded, Kommersant reported.
The website of the organization Rosuznik, which defends the rights of jailed civil activists, describes Sobolev as a hard-line nationalist who went on trial in 2010 as an alleged member of neo-Nazi group White Wolves, which took part in attacks against migrant workers. Sobolev was acquitted by a jury in the case.
Arkhipenkov, who worked for a tourist agency, spent time in jail on drug charges in 2009 after being arrested by Ecuadorian police for trying to smuggle drugs into that country.
Investigators said 11 people arrested in connection with the violence on Bolotnaya Ploshchad remain in detention.
Opposition leaders have said authorities intended to provoke the May 6 clashes by purposely blocking entrances to the square where the rally was to be held. The confrontation between police and demonstrators began after a bottleneck formed at the entrance to the square.
Opposition activists have announced plans to picket the Investigative Committee building every week until activists arrested in connection with the May 6 violence are released.
After demonstrators who included opposition leader Sergei Udaltsov gathered at the building last week, police ordered Udaltsov to appear in court Thursday to face misdemeanor charges of organizing an unsanctioned demonstration, Interfax reported. He could be forced to pay a 30,000 ruble ($940) fine if found guilty.
Udaltsov told the news agency that protest organizers haven't sought authorities' permission for the pickets, which is required by law, since their last request to protest was ignored.