Two 15-year-olds, a boy and a girl, have been robbed by a man brandishing a Stanley type knife.
The incident occurred at around 2pm yesterday afternoon as the pair were walking across Town Fields when they were approached by a man on a bike. The man produced a Stanley type knife and demanded phones and money from the two teenagers.
He then rode off along Lawn Road towards Thorne Road.
Police believe he travelled along Thorne Road towards Doncaster before turning on to East Laithe Gate.
The man is described as being white, in his 30s, wearing a grey beanie hat and black scarf over his face.
He was riding a silver mountain bike with an orange logo.
Officers would like to speak to anyone who witnessed the robbery or saw the offender as he left the scene.
Anyone with information about the incident is asked to call South Yorkshire Police on 101 quoting incident number 573 of 24 January 2015.