A teenage girl is believed to have been sexually assaulted on three separate occasions as she walked home from a night out.
Police say the 17-year-old was repeatedly attacked over the course of an hour after she became separated from her friends following a visit to a club in Tower Hamlets, east London.
Her ordeal is said to have begun just before midnight on Friday 29 September and ended nearly two hours later.
Police have released CCTV footage of two of the suspects and are appealing for anyone with information to come forward.
CCTV, which police say is too grainy to release, show a man carrying the girl in Cambridge Heath Road, close to Bethnal Green station, towards a doorway.
While the man is not picked up by CCTV again, the top half of the girls’ clothes are seen removed.
Minutes later, cameras show the girl stumbling down Mill Street, police say, followed by a different man – he has a beard and is on a bike.
Footage shows the man approaching the girl in Corfield Street, directing her to an area away from the street, where they remain for a period of time before he leaves.
The girl, whose clothing appears dishevelled, emerges shortly afterwards and goes further down Corfield Street.
Just minutes later, at around 12.45am, detectives believe the victim suffered a third attack, possibly involving two or three men.
The CCTV captures a third, different man walking down Corfield Street and joining two other figures under some trees.
He appears to bend down towards a spot on the kerb in between some parked cars.
Detectives believe it was at this point that the victim was sexually assaulted.A short time later, a member of the public spotted the teenager lying on the ground in Corfield Street in a state of distress and called 999.
Detectives believe it is possible that she was drugged and are in the process of carrying out toxicology tests.
Detective Inspector Suzanne Jordan, from the Metropolitan Police's child abuse and sexual offences command, said: "This is a horrific multiple sexual assault on an young female who was simply making her way home after a night out.
"We believe two of the three were very serious sexual assaults indeed, and are determined to catch the persons responsible for these hideous crimes.
"I would urge anyone who recognises either male in these images to contact us as a matter of urgency."
Anyone with information should contact the Metropolitan Police on 101, via twitter at @MetCC, or by calling Crimestoppers on 0800 555 111