Investigators in Russia said Wednesday they had made another arrest in an ongoing probe into anti-Putin protests on Moscow's Bolotnaya square in May that led to violent clashes.
Ilia Guchin, 24, is accused of blocking police from arresting another protester at the demonstration in central Moscow on May 6, on the eve of President Vladimir Putin's return to a third term in the Kremlin.
The protest erupted into violent street battles between riot police and the opposition, leaving around 30 police officers and dozens of protesters injured.
The Investigative Committee said it had identified Guchin from video footage.
"On May 6, at Bolotnaya square, grabbing a policeman by his uniform and trying to pull him down, (Guchin) obstructed the arrest of another protester at the riots," the committee said.
A total of 19 people are being prosecuted for last year's events, 12 of whom are in pre-trial detention. They each risk 10 years in jail.
One man was already handed a sentence of four-and-a-half years in November.
"Not a single one of the organisers or participants in these mass riots on Bolotnaya square... will escape his criminal liability, that's why the work of identifying (protestors) continues," investigators said.
A number of opposition leaders including anti-corruption blogger Alexei Navalny and leftist radical Sergei Udaltsov were arrested and later released.
In a declaration posted online on January 29 by Russia's presidential council on human rights, an advisory body to the Kremlin, 26 of its 62 members believed the attitude of security forces had caused the trouble, and rejected the term "riots" as unjust.
The declaration said justice "should not be about settling of political scores but instead bring cohesion to society".
Putin opponents claim the clashes were a retaliatory crackdown on protesters after an estimated 50,000 people gathered to demonstrate in the capital in December 2011.