Eight women were sexually assaulted near Clapham Common, south west London, in the last three weeks - with two men being arrested in connection with the incidents on Tuesday and Thursday.
However the serial rapist appears to have struck again this weekend, with another young woman being targeted.
The attacks all involved women in their 20s and 30s who were alone in the area late at night.
Each victim has described the offender as being of Mediterranean or middle eastern in appearance, with dark hair.
In one terrifying assault, which was partly captured on CCTV, the man attacked one woman as she was trying to let herself into her house.
Chief Inspector Tony Hirst said: ‘At this early stage, it is being linked to the previous eight assaults.
‘I would like to reassure the public that we have increased police patrols in Clapham and Brixton Hill areas. Detectives continue to study CCTV and are following up a number of active leads.’
The police chief added that women should remain vigilant, be aware of their surroundings and ‘trust their instincts’ - and that if an individual caused them concern they should call the police.
Two men who were arrested in connection with the crimes have been released on bail.