A man has been left with serious injuries after he was assaulted on Waverley Bridge in Edinburgh.
The 25-year-old had been walking with two friends in the centre of the city at about 03:30 on Sunday when he was attacked.
He is being treated for head and facial injuries at Edinburgh Royal Infirmary, where he is described as being in a serious condition.
Police officers investigating the attack have appealed for witnesses.
The suspect is a white man in his early 20s. He is described as being of average build with short dark wavy hair and was thought to be wearing a beige or brown T-shirt.
He is thought to have been with three or four other men, of a similar age, all of whom witnessed the incident.
Det Con Graham McIlwraith said: "This was a violent and frightening attack for the victim and we are eager to trace the man responsible as soon as possible.
"I would ask anyone who was in the Waverley Bridge area in the early hours of Sunday morning, and saw either the incident, or the man and his companions in the vicinity, to please get in touch with us immediately."