Andrei Balin, the co-chairman of the local branch of the Republican Party of Russia – People's Freedom Party in the central Russian city of Talyatti, was beaten and robbed shortly before the party's leader, Boris Nemtsov, was gunned down in Moscow.
Balin was attacked as he was returning home on the evening of February 27.
The unknown assailants assaulted Balin near the entrance to his building and stole his laptop computer.
Balin regularly posted material on his Facebook page that was critical of the policies of the Russian government, in particular President Vladimir Putin.
Police said they believed the assailants aim was to steal Balin's computer, which had information on Balin's contacts and activities.
There was no indication that authorities were treating the incidents as related.