POLICE are hunting a teenager they believe responsible for a spate of robberies in Watford this week.

At 3.30pm on Monday, the youth threatened a 15-year-old boy with a knife before stealing his mobile phone in Lady's Close.

Between 1.20pm and 1.30pm, three boys were threatened with CS gas and a knife in Harwoods recreation ground, Holywell, by the youth, who stole a mobile phone and iPod. Just after 1.20pm, a 15-year-old boy and his friends were in Hagden Lane park when they were approached by the youth on his bike.

He threatened them with CS gas and demanded their mobile phones.

And at about 2.50pm, the man approached a 17-year-old boy in Water Lane and brandished a knife in order to get his phone. The youth is described as Asian, aged in his late teens to early-20s and wore a hoodie in all of the incidents.

He was riding a mountain bike on Tuesday and was carrying a canister.

He has also worn dark blue jeans and a black scarf covering his nose.

Detective Sergeant Joe Quinlivan said: "It is very rare for Watford to experience so many robberies in such a short space of time and I would urge teenagers to keep their personal belongings out of sight." Anyone with information about the robberies should telephone 01923 472494, 08453 300222 or 0800 555111.