Detectives investigating a string of sexual assaults on teenagers travelling on buses in north London have released pictures of the suspect.

Two 14-year-old girls are among four alleged victims who were assaulted over a seven week period earlier this year.

The first assault occurred after the attacker boarded the 279 bus at Tesco Ponders End at 6.30pm on January 25.

He sexually assaulted an 18-year-old woman when she was standing up and later sitting down before he got off the bus at Angel, Edmonton.

He struck again four days later at 7.20am when he sexually assaulted a 14-year-old girl on the same bus after boarding at White Hart Lane.

And on February 21 at 7.45am he boarded the 279 bus again, this time at Nightingale Road, before subjecting a 14-year-old girl to a sexual assault.

Weeks later on March 12 a 15-year-old girl was assaulted on the 34 bus after boarding at Cambridge Roundabout.

Three days later, shortly before 9am, a 17-year-old girl boarded the 102 bus at Fortismere Avenue heading towards Bounds Green. Sitting upstairs, the teenager witnessed the suspect playing with himself while watching her as he sat nearby.

The suspect has short black hair and a thin beard along his jaw. He was wearing a two-tone padded blue jacket and blue jeans.

Detective Sergeant Edward Coleman, leading the investigation is urging any other victims to come forward.

"We know of at least five offences committed by the same suspect on crowded buses,” he said.

“We would like to hear from anyone who may know this man's identity.

"We also want to hear from anyone who may have been the victim of a sexual assault while travelling on a bus."

Anyone with any information is asked to call DS Edward Coleman on 020 3054 6710 or 101 quoting reference CAD 2343/12Mar or tweet @MetCC.

To call anonymously, please contact Crimestoppers on 0800 555 111.