The assaults took place just five days apart in Plaistow South, in Newham, and Amethyst Road, in Waltham Forest.
Both women, aged in their early 30s, were also robbed by the suspect.
Police have now released an image of a man they are keen to trace as part of their investigation.
Detective Superintendent Andrew Packer said: “These incidents have been deeply traumatic for the victims, who are being supported by specialist officers. My teams are completing a detailed review of all the facts available so far. In addition to a dedicated investigation team we have extra patrols in the area to provide reassurance and these officers are actively seeking to arrest this suspect.
“Please have a good look at this photo , and let my officers know if you have any idea as to who this man is.
“I would advise any women walking alone at night to remain vigilant, to be mindful of their surroundings, and to keep family and friends informed of where they may be going. If you see anything you think is suspicious, do not hesitate – call 999 immediately.”
Police said the first incident took place at 2.40am on Monday, July 1, when a 35-year-old woman was approached from behind by a man while walking home.
He then raped her and stole property belonging to the victim.
The second incident took place on Saturday, July 6 at Amethyst Road, Waltham Forest at 4.20am, when a 31-year-old woman was approached by a man who then raped her. The man also stole property.
Detective Superintendent Packer added: “I would advise any women walking alone at night to remain vigilant, to be mindful of their surroundings, and to keep family and friends informed of where they may be going.
“If you see anything you think is suspicious, do not hesitate – call 999 immediately.”
Anyone who can identify the man is asked to call the investigation team on 07881 330951.
Alternatively call 101 or tweet @MetCC quoting CAD 777/1 July. You can call anonymously on Crimestoppers 0800 555 111