POLICE are trying to trace two men who intervened in an unprovoked and vicious assault.

The men jumped out of a Ford Transit van after seeing the attack in King Street, Blackburn, outside the newsagents.

Police said a 21-year-old man had been head-butted and punched in the face. He was on the floor being beaten as the men approached.

They challenged the attacker and said: "Don't you think he has had enough?"

The attacker then fled and the victim was taken to Blackburn Royal Infirmary, where he was detained overnight. He has a suspected hairline fracture to his skull and bruising.

Detective Constable Adrian Lewin said: "It was a totally unprovoked assault on a busy street. There will have been other people who have been around at the time and we would like to speak to them."

The men were only described as white and came from a white transit van with red writing on the side.

Police said the attacker was white, 6ft tall and of an athletic build.

The incident happened at 1pm on Wednesday.

Call DC Lewin on 01254 353569 or Crimestoppers on 0800 555 111 with information.