The investigation is continuing into a serious assault inside a house on Shearer Road in Portsmouth on Monday evening.
Officers were called just before 7pm after a 17 year-old girl had been assaulted with a weapon believed to be a hammer, leaving her with a serious head injury.
She was taken to Southampton General Hospital, where she remains in a serious but stable condition.
Detective Inspector Liam Davies said: "We are actively trying to identify a man seen running across Shearer Road and into Beecham Road past the Shearer Arms Public House at 7pm. We are releasing an image of this man in the hope of speaking to him, as he may be able to assist our enquiries. This image is not of the best quality, but indicates where he was and which direction he was walking in. We are treating this as an isolated incident at this time.
"A number of active lines of enquiry are being followed, but I'd urge anyone who saw anything suspicious in the area between 4pm and 7:30pm to contact us".
The man shown in the CCTV image is described as:
5ft 5ins tall.
He has short light brown hair and a short beard.
He was wearing a brown coat, jeans, and light coloured trainers.
Superintendent Will Schofield who is charge of policing in Portsmouth said: "Officers from across the city and other areas of Hampshire and the Isle of Wight are working tirelessly to progress this investigation to secure justice for the victim. This is a shocking incident, but I'd like to re-assure the local community that we are actively patrolling the area and these officers are happy to address any concerns that you may have if you speak to them‘.