Campaign workers for Russian opposition politician Aleksei Navalny say a group called Otryady Putina (Putin's Brigades) attacked Navalny's local headquarters in the city of Krasnodar on August 3.
Navalny's campaign workers posted messages online saying the attackers were mostly elderly women.
They said the attackers broke a window and the main door to the opposition figure's headquarters.
One of the attackers, a young woman, was taken to a hospital by an ambulance.
The opposition activists said another attacker, a young man, was caught by police inside Navalny's Krasnodar office but was released after briefly being questioned.
The attack came a day after an unknown vandal painted the words "Putin -- Fascist" on a building that houses an office for Putin's Brigades.
Navalny's staff in Krasnodar said they had nothing to do with the graffiti.
Navalny campaign workers say members of Putin's Brigades forced their way inside of the opposition politician's Krasnodar headquarters on July 31, tearing up posters and overturning tables and chairs.
They said the attackers also nailed wooden planks onto the office door.
Anticorruption blogger Navalny is actively campaigning for the March 2018 presidential election, in which President Vladimir Putin is widely expected to seek and win a fourth term.