DETECTIVES are appealing for witnesses after a teenage girl was sexually assaulted by two youths.

The victim, a 15-year-old black girl was chased by two teenage black boys in the Woolwich Common estate.

The chase began at around 9.15pm in the evening and the victim was caught and sexually assaulted by both boys.

Officers are very anxious to trace a black woman with extensions in her hair who stepped out of the victim's way as she was running away from the boys.

They also want to speak to a white woman who was walking with a black dog on the common. The dog chased the girl as she was running and had to be called back by its owner.

Detectives believe the women may hold vital information in relation to the August 20 assault.

A police spokesman said: "Are you one of these ladies or do you know them? Detectives wish to make it clear neither of these ladies are suspected of any crime.

"They are known to have seen the girl running away and may have seen the suspects."

Detective Marie Marshall from Greenwich police's Sapphire Unit, which investigates sex crimes, said: "This was a terrible crime which had a devastating affect on the life of the young victim.

"I urge anyone with information to contact 020 8284 9818 or Crimestoppers anonymously on 0800 555 111."