Kent Police is appealing for witnesses after a man was robbed by a group of three men in an alleyway in Chatham.
The unprovoked attack took place in Jenkins Dale after 10pm on 3 February.
Then, the victim walked past two men talking before he was punched in the back of the head.
He was then grabbed by a man who kneed him in the head after he turned to confront the two men.
A third offender, who was standing nearby, then joined the other two men in the alleyway and they all started to punch, knee and elbow the victim repeatedly.
During the assault, the victim heard someone shout and one of the offenders ran towards the voice and spoke to them before returning and continuing the attack.
After stealing the man's leather jacket, which contained his mobile phone, the three ran off in the direction of Chalkpit Hill.
Detective Constable Stuart Clayton, of Kent Police, said: 'This was an unprovoked attack in which the victim received a number of cuts and bruising to the face, as well as a broken nose.
'We are particularly keen to speak to the person that shouted out during the assault and spoke to one of the three men. I would urge them to come forward and help us with our enquiries.'
One of the offenders has been described as a white man, aged between 17 and 22, 5ft 8ins tall, clean shaven and with short blonde hair and wearing a white baseball cap, grey matching tracksuit top and bottoms.
The second offender is described as a black man, aged between 17 and 22, 5ft 7ins tall, heavy build and with distinctive dark spots on his cheek. He was wearing a matching black tracksuit with a gold stripe down the arms.
The third offender was a white man, aged between 17 and 22, 5ft 7ins tall, athletic build, clean shaven and was wearing a dark jacket, dark coloured baseball cap, blue jeans and white trainers.
If anyone has any information call DC Stuart Clayton on 101, quoting reference XY/3963/13.
Alternatively contact Kent Crimestoppers anonymously on 0800 555 111.