Women are being warned to stay alert as police say they are linking three violent attacks in south London in the past few months.
The assaults were on women walking alone in the early hours of a weekend or public holiday and took place within a four-mile radius of each other.
Each time, the victims were surprised from behind before being physically assaulted.
On Friday, 4 December, a 31-year-old woman was left with a head injury after being attacked on Commercial Way, SE15, between 1.15am and 2.15am.
On Sunday, 13 December, a second woman, aged 30, was assaulted to the point of unconsciousness on Hanover Park, SE15, between 6.15 am and 6.45am.
She was found lying in the street.
The third victim was attacked on New Year's Day in Creekside/Deptford Church Street, SE8.
The 18-year-old was left with serious assault injuries to her head and face.
Police say the assaults were previously being looked at separately but intelligence work led to them being linked.
A spokesman said that, while there is currently no evidence that the attacks were sexual, all three are being investigated by the Sexual Offences, Exploitation and Child Abuse Command's Serious and Complex Case Team.
Detectives have released a CCTV image and footage of a man they would like to find and speak to in connection with the offences and warned women to be careful.
Detective Chief Inspector Zena Marshall said: "The level of violence appears to have escalated each time so I am urging women, in and around the areas affected, to be alert and follow personal safety advice."
She said the attacker may have struck previously and encouraged any women who had been approached or assaulted in similar circumstances to contact police.
"Also, I would urge anyone who thinks they recognise the man in the CCTV image released to contact us.
"Any information you have could prove vital in enabling us to identify and speak to this man as part of our investigation.
"I would also urge anyone who was in any of these locations on the days and times of these offences and saw something that may help then please get in touch with us."