POLICE are warning youngsters to be extra careful after a gang pretending to sell goods snatched a mobile phone from a teenager.

The 15-year-old victim was threatened with violence before he handed over his mobile in what police described as a "worrying robbery".

A gang of three white males made contact with the boy by pretending to sell a mobile phone top up card as he wandered around Blackburn town centre market .

The boy tried to walk away away but the thieves persisted and followed him to nearby Whalley New Road.

They then became aggressive and threatened the boy with violence, demanding he hand over his Motorola phone and some cash.

PC Steve Finley of Blackburn police said: "Fearing for his safety, the boy had no choice but to hand over the phone. They made off with the phone and a small rubber pouch and ran off back towards the town centre."

More than 180 mobile phones were reported stolen in the first two months of this year in the Eastern Division which covers Hyndburn, Blackburn and the Ribble Valley.

PC Finley added: "We are very concerned by mobile phone crimes but they are very difficult to predict.

"These crimes are very sporadic and although we do not believe any one particular group to be in operation, we advise anyone using a mobile phone to keep it concealed when they are in busy places."

One of the offenders, thought to be 17-years-old, was described as 6ft tall, wearing a yellow and blue jester's hat with a track suit top.

The second robber, also thought to be 17, is described as 5ft 6in tall with curly brown hair and having bags under his eyes.

The third assailant is said to be in his thirties, around 5ft 6in tall of skinny build, with a skin head.

In a bid to reduce mobile phone crime, the police have also teamed up with phone stores in East Lancashire to provide a free ultra violet coding mark on phones.

Under the scheme anyone can go into designated shops and have their phones security marked, making tracing mobile phone owners, in the event of a robbery, easier.