Teenage gangs are threatening to attack youngsters with golf clubs and screwdrivers unless they hand over their expensive mountain bikes.
On one occasion an 11-year-old boy was hit across the back with a club before being forced to give his bike to four youths in Broadmayne, Basildon.
The young victim is now receiving counselling from experts to help him get over the ordeal.
And just 45 minutes later in Southernhay, Basildon, a 15-year-old was told by two youths to hand over his bike or he would be stabbed with a screwdriver.
Detectives are linking the incidents and believe the hi-tech Y-framed bikes will be resprayed and sold to someone looking for a cheap Christmas present.
Last week a 16-year-old needed hospital treatment after he was pushed to the ground and kicked about the head before being robbed of his bike.
The youngster was left with bruising to his face and body following the terrifying incident at Beambridge, Pitsea.
Det Con, Darren Jones, of Basildon CID, said: "We are very worried. The gangs are only teenagers themselves who are threatening children with dangerous weapons.
"We are talking about aggravated robbery which is a very serious crime. We are treating this just as seriously as any other robbery."
Anyone with information is asked to contact Det Con Jones on 01268 244010.
By Glenn Cordingley
Reporter's e-mail: glenn.cordingley@notes.newsquest.co.uk
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