The Pussy Riot punk group has been attacked in Sochi by Cossacks wielding whips and pepper spray, as they were about to perform a song.
Eyewitnesses said members of the group had just put on their trademark brightly coloured balaclavas in a restaurant in downtown Sochi in preparation for the performance.
But when they left the restaurant they were set upon by around a dozen Cossacks - local militia who are used by police to help patrol the town, AP reported.
One Cossack smashed their guitar, and others tried to rip off the group's balaclavas.
Group member Nadezhda Tolokonnikova tweeted that "Cossacks attacked us, beat us with whips and abundantly sprayed us with pepper gas".
Another band member, Maria Alyokhina, tweeted a photo of a man with a bloodied face.
She said the man was a member of Pussy Riot, and had a "cracked eyebrow after the attack of the Cossacks"
She also tweeted photographs of what she said were bruises on her chest left by the batons of the Cossacks, and a ripped fingernail.
A local activist associated with the group said the male member of Pussy Riot had been "brutally beaten" by the Cossacks.
In Russian, David Hakim said the Cossacks had used pepper spray and beaten them with whips.
His account was backed up by a reporter for VICE News, Simon Ostrovsky, who said "group of Cossacks just thrashed Pussy Riot in Sochi with whip handles and pepper spray".
He said one of the Cossacks had been detained.
However, AP reported that when police arrived and questioned witnesses, no-one was arrested.
On Tuesday, members of Pussy Riot were detained for three hours by police, reportedly for questioning over a theft at a local hotel.
They said they were in Sochi to perform a song called Putin will teach you to love the motherland.
It was "dedicated to prisoners of the swamp [referring to a May 2012 political protest that turned violent in Moscow's Bolotnaya Square], corrupt Olympics, ecologist Vitishko and suppressed freedoms in Russia".
According to some news reports they were also filming a video clip for the song.
Activist filmmakers Gogol's Wives, who have been following Pussy Riot, Tweeted late Tuesday night that a Cossack had been walking with a whip around the hotel where they were staying.
On Wednesday morning the IOC warned Pussy Riot not to come to the Olympic park for any political demonstration.
After the arrest on Tuesday there were some reports that they would try to perform at the Olympic park, half an hour away.
"If they did it would be wholly inappropriate," said IOC spokesman Mark Adams.
A local activist later tweeted a photo of Pussy Riot, apparently recovered from the attack, performing in front of the Olympic rings outside the local administrative offices in Sochi.
- Sydney Morning Herald