Teenage boys forced to perform a gay sex act with each other by a man who threatened them with a knife

Two teenage boys were forced to perform a gay sex act with each other by a man who threatened them with a knife.

The victims were also made to fight with each other and steal from a nearby shop.

The boys' horrific ordeal began when they were approached by a man on a double decker bus at Brixton in south London.

Police said they were taken to a park where they forced to fight before one of the boys was made to perform a sex attack on his friend in the stairwell of a block of flats.

Detectives from Scotland Yard's Sexual Offences Exploitation and Child Abuse Command released a CCTV image of the suspect.