Openly bisexual Right Said Fred singer Richard Fairbrass was reportedly punched in the face and kicked during a gay rights march in Moscow.
The demonstrators were protesting a ban on another march scheduled to mark the 14th anniversary of Russia decriminalising homosexuality.
Neo-Nazi protesters pelted demonstrators with eggs and chanted, "Moscow is not Sodom" and "Death to homosexuals."
The gay activists, who included high-profile rights campaigner Peter Tatchell, were trying to deliver a letter signed by 40 European politicians to the office of the Moscow Mayor Yuri Luzhkov.
Luzhkov imposed the ban on the anniversary march and described such gatherings as "satanic."
When trouble broke out, Moscow police arrested about a dozen demonstrators and forced them into a bus.