Video of a street attack which led to a large crowd gathering round the fracas is being sought by police.
Officers from Durham Constabulary are investigating the incident, which happened in Saddler Street in Durham on Sunday at 8.20pm.
It happened close to Fabio's Bar and La Spaghettata where police say a man assaulted door staff and was restrained on the floor.
A police spokesman said: "The man was wearing a white t-shirt and was soaked in blood.
"There was a large crowd gathered around him, some of whom were recording the incident on their phones.
"We are appealing to these people to come forward."
Anyone who witnessed or recorded the incident is asked to contact Detective Constable Alistair Rogowski on 101.