Six group members — five women and one man — donned their signature ski masks in central Sochi and were pulling out a guitar and microphone when at least 10 Cossacks and other security officials moved in.

One Cossack appeared to use pepper spray. Another whipped several group members while other Cossacks ripped off their masks and threw the guitar in a rubbish bin.

“A few seconds into the song they began to beat us with batons and pepper spray us. We didn’t even get through the first verse of the song,” band member Maria Alekhina said.

The Cossacks violently pulled masks from the women’s heads, beating group member Nadezhda Tolokonnikova with a whip as she lay on the ground.

The incident lasted less than three minutes and one Pussy Riot member, a man wearing a bright yellow tank top, was left with blood on his face, saying he had been pushed to the ground.

“They hit me all across my body, look at my bruises,” Tolokonnikova said.

Krasnodar region governor Alexander Tkachev, who has been advancing Cossacks’ interests for years, promised to conduct a “thorough probe” into the incident and prosecute the attackers.

Pussy Riot, a performance-art collective involving a loose membership of feminists who edit their actions into music videos, has become an international flashpoint for those who contend President Vladimir Putin’s government has exceeded its authority, particularly restricting human and gay rights.

The group, which called for a boycott of the Sochi Olympics, gained international attention in 2012 after barging into Moscow’s main cathedral and performing a “punk prayer” in which they entreated the Virgin Mary to save Russia from Mr Putin, who was on the verge of returning to the Russian presidency for a third term. Two members of the group, Tolokonnikova and Alekhina, were sentenced to two years in prison but were released in December.