The incident happened in Central Park off Petersfield Avenue around 7.30pm yesterday (April 8).
During the incident the victim was assaulted, leaving him with injuries – the details of which are not known.
There have been no arrests but police enquiries into what happened are ongoing.
A Met Police spokesperson said: “Police were called to a report of an assault and a theft in Central Park, off Petersfield Avenue, Harold Hill at around 19:21hrs on Tuesday, 8 April.
“A boy suffered minor injuries during the incident and reportedly had a bike stolen.
“Enquiries are ongoing and no arrests have been made at this time.
“Anyone who witnessed the incident or had any information or footage is asked to call 101 or post on X @MetCC quoting CAD 6452/08Apr.”
