Nikolai Kavkazsky, a key defendant in the series of trials against Russians who participated in a May 2012 demonstration at Moscow's Bolotnaya Square, has been attacked and beaten by two unknown assailants.
Kavkazsky posted the information on his Twitter account, saying one of the men had fled the scene in a car, while the other ran into a nearby residential building.
He told RFE/RL that the men were drunk and they attacked him as he was campaigning for a seat on a municipal council from the Yabloko party.
He said the men attacked and struck him about 30 times after they saw the Yabloko campaign materials in his hands.
He was not seriously injured.
Kavkazsky was accused of participating in mass disorders in connection with the Bolotnaya protest, but the charges were dropped in 2013 under the terms of an amnesty. He maintains his innocence.