TEENAGERS were today placed on red alert against knife-wielding street robbers who are threatening their young victims.

The warning comes from detectives in Accrington just days after police in Blackburn urged students in the town to be on their guard following two similar incidents in a week.

Officers think an organised gang may be behind them as the robbers use the same trick.

They tell their victims they look like people who have attacked or stolen from relatives, before marching them from the scene and robbing them, sometimes at knifepoint.

In Blackburn, two teenagers were told they fitted the description of people who had attacked a cousin before being walked to the Whalley Range area of the town, threatened with a knife and forced to hand over cash and bank cards.

The first attack in Accrington occurred after two youths aged 16 or 17 approached a 17-year-old at the railway station off Blackburn Road and marched him to a nearby street before searching him and snatching his mobile phone.

A 15-year-old had £26, a Timberland watch and a Nokia mobile phone stolen after he was also approached at the railway station.

Detective Sergeant Mark Rothwell, of Accrington CID, said: "These attacks are causing us grave concern because they are obviously being carefully planned with the same story used every time.

"We are linking these four robberies but we don't know if there have been any more incidents and we would urge people not to be fooled by the story and to call the police if they find themselves approached by them."

One of the thieves operating in Accrington is Asian, 6ft and of medium build with a moustache and mole under his left nostril. He has a slim face.

The second is also Asian, around 5ft 8ins and with numerous scars on his forehead and cheek. His teeth were yellow and his front tooth chipped.

The Blackburn mugger is aged between 18 and 25, 5ft 8in or 5ft 9in tall and of medium build with straight black hair, stubble and a goatee beard.

Anyone with any information about the attacks can contact Accrington Police on 01254 382141, Blackburn Police on 01254 51212 or Crimestoppers on 0800 555 111.