A good Samaritan helped fight off a gang who attacked a man and slashed his face in Oxford.

Police want to trace the man who came to the aid of the 21-year-old victim and his partner after they were attacked by around 15 youths in Blackbird Leys.

The couple had been at the Bowlplex at the Kassam Stadium and were walking along Windale Avenue when the yobs confronted them just after 1.30am on Saturday, shouting verbal abuse.

The man was punched in the face and was taken to the John Radcliffe Hospital in an ambulance. He needed stitches to a four-inch gash in his left cheek.

Police spokesman Tim Wiseman said: "They were set upon by a number of people from the group and assaulted. The man received a cut to his cheek caused by a knife or broken glass.

"A black man came to their aid and was involved in the fight, possibly receiving an injury to his leg. He left no details and left soon after the incident."

Pc Simon Gray, of Cowley Police Station, added: "I am appealing for witnesses to either this group of youths or the incident itself.

"I am also keen to trace the brave man who helped this couple, both as he may be an important witness and also because I need to check his welfare."

Anyone with information can contact Pc Gray on 08458 505505 or Crimestoppers on 0800 555111.