Nine females - three aged 11 - have been approached and sexually touched by an attacker in the last three months, police said.
Two women aged 27 and 25, and seven children aged 11 and 13, have been approached by a man who assaulted them before fleeing on foot in the Greenwich and Lewisham areas of London.
All nine attacks took place in broad daylight between June 30 and October 16 with three taking place within half an hour on October 5, officers said.
Police are considering the possibility that all the attacks are linked and have released CCTV of the latest incident - in Honor Oak Road on Monday at 4pm - in a bid to help identify a man.
Superintendent Lee Hill of Greenwich Police said: "These incidents were very frightening for the victims. I am appealing to the public to help identify and locate this man as quickly as possible.
"Although none of the victims have suffered physical injury, the effects of becoming a victim of sexual assault can be lasting and traumatic.
"There is a possibility that these incidents are part of a linked series of attacks as a number of victims have provided very similar descriptions of the attacker - a white man aged between 40 to 50 years old, with short white or blonde hair. This is one line of inquiry detectives are exploring."
Scotland Yard said patrols in the areas have increased and officers are speaking to local schools to reassure pupils and parents.
Mr Hill added: "I am concerned that there may be more victims who have not yet come forward and are not receiving the support that they may need. I would urge any victims who have not yet come forward to contact police."
Anyone with information is asked to call police on 101 or Crimestoppers anonymously on 0800 555111.