Detectives investigating an attempted rape have put up a £10,000 reward for information.
They have also released CCTV footage of a man on a bike who they are keen to trace in relation to the attack, which took place at around 2.05am on Saturday, June 17.
A woman was followed and pushed into an alleyway in Harrow Road, Leytonstone, where she was attacked.
Enquiries have found that the suspect was seen in the area around Maryland station close to the time of the attack.
The woman, 26, required hospital treatment and is receiving specialist police support.
Detective Inspector Jimi Tele said: “The victim of this crime was alone and on foot when she was targeted by a man who followed her for some time before his attack.
“One line of enquiry we are investigating is if he followed other women, and possibly approached at least one other woman, in the local area prior to this attack being carried out.”
He described the suspect as being of Somali appearance, aged between 20 and 30, of very slim build and with a high hair line.
He added that the suspect was riding a distinctive bike with narrow handlebars and white wheels, which had white rims and white tyres.
Det Insp Tele added: “I would appeal to anyone who believes they recognise this suspect from the images to contact police, or anyone who was in this area and believes they may have seen or been approached by this suspect to contact us.
“I am particularly interested in tracing possible witnesses who may have been approached by this suspect or can offer any information which may lead police to his identity.”
Anyone with information is asked to call police on 101 or Crimestoppers anonymously 0800 555 111 or by tweeting @MetCC.
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