Dozens of local and foreign gay-rights activists were attacked on Saturday by Russian nationalists when they defied a ban and held a march in Moscow.
More than 100 people were arrested, according to police cited by the Interfax news agency.
Nikolai Alekseyev, leader of the gay rights organization GayRussia, was among those arrested as he and supporters attempted to approach the Tomb of the Unknown Soldier near the Kremlin to lay flowers, in a symbolic protest equating the fight for gay rights with the war against Nazi Germany.
"The entrance to the park was closed when we got there and there was a crowd of people outside, what most people would call neo-fascists," said Robert Wintemute, a professor at King's College in London and one of the foreign gay activists who took part in the protest.
"There was a scuffle and then I saw police taking Nikolai Alekseyev away and putting him in a police van. After that, neo-fascist thugs started running wild here and there. Thugs kicked Merlin Holland, the grandson of Oscar Wilde. I've never seen such things," Wintemute said.
Volker Beck, a German Bundestag deputy, had blood on his face after being hit.
Pilippe Lasnier, who was heading a delegation from the office of Paris Mayor Bertrand Delanoe, was briefly arrested.
"At the moment when Russia is taking over the presidency of the Council of Europe we are concerned because the Russian authorities haven't shown the will to respect human rights, in particular the rights of minorities and freedom of expression," said Clementine Autain, one of Delanoe's aides.
Regular Moscow city police reinforcements backed by several hundred OMON special anti-riot police tracked gay activist protesters and hundreds of nationalists ranging from "skinheads" to members of Cossack and Orthodox Slav groups along a main avenue in Moscow.
There were minor scuffles at various places on the street but reporters said the confrontation between the gay activists and their opponents was mainly limited to aggressive posturing and shouting of insults, including "Moscow is not Sodom" by the hardline nationalist supporters.
But bands of skinheads attacked the gay-rights activists in front of the mayor's office, where they had hoped to leave a letter protesting the ban on the gay pride march.
Reporters saw police detain dozens of young nationalists and one Russian news agency reported that dozens of gay activists were also detained, though this report could not be confirmed.
Moscow Mayor Yury Luzhkov had banned gay activists from holding a parade in the city center, a decision supported by Russian religious groups and upheld by a court where it was challenged on Friday. Luzhkov had said such a march was morally "inadmissible" because people should not publicly display their "deviations in the sphere of organization of life and sex."
Protest organizers had said they would try to hold two demonstrations in defiance of the ban.
"Homophobia is part of the larger problem of xenophobia" in Russia today, Alekseyev said at a news conference."This country defeated fascism and today it is again on the rise."