Radiohead have said their "hearts go out" to fans attacked during a listening party in Istanbul.
The band held a streaming event with record stores across the globe to celebrate the release of their new album, A Moon Shaped Pool.
But a violent attack broke out at the event at Velvet IndieGround Records on Friday evening, where fans had gathered to listen to the live audio stream.
The event was streamed on Periscope, and so was caught on camera - with footage uploaded to YouTube.
Radiohead said in a statement: "Our hearts go out to those attacked tonight at Velvet IndieGround in Istanbul.
"We hope that someday we will be able to look back on such acts of violent intolerance as things of the ancient past.
"For now, we can only offer our fans in Istanbul our love and support."
It has been reported in the local media that the attack came from Islamic extremists objecting to people drinking alcohol and playing music during the holy month of Ramadan.
In the video, a man can be heard shouting in Turkish: "Let's see you drink in the month of Ramadan again."
Attackers are shown entering the shop, shouting "close this place down" and "who the f*** is running this place".
There is a noise of bottles breaking, and someone screams: "Please do not hit."
A man enters the store, saying: "Get the f*** out, close this place down, I'll kill you, I mean it, I'll kill you... I'll burn this place with you inside."
It is unknown how many people were injured in the attack, or the severity of their injuries.
One of the event hosts allegedly posted about the encounter on Reddit, saying: "I am the person that's speaking in that video. I am the owner of that Periscope account.
"They were determined to kill us. We were beaten by more than 20 men with pipes in their hands, beer bottles were broken on our heads. I don't even know how we made it out. I will share the details later guys, just hoping that no one will die."
He later added: "I love you all. Looks like everyone at our event is fine. For the first time in my life, I was scared of being killed. Can't even think right now, just a blank stare at the walls.
"Weird Fishes is my favourite song in the world, and I was dancing to it outside when it all started. Now it has so much more meaning for me."