A 14-year-old boy was hurt when he was threatened with a knife and robbed in a shopping centre by a group of teenagers.

The Gillingham boy was in Marks and Spencer at Bluewater shopping centre, Greenhithe, with his friend at around 3.30pm yesterday when a group approached him and started harassing him.

The teens, who are believed to be around 16 to 17, started grabbing at the boy's necklace and trying to take it from his neck.

The gang managed to unhook the necklace - and because he held onto it so tightly he was left with a cut on his finger.

His mother, who asked that her son remain anonymous, said: "I'm in complete shock that passers-by watched and did nothing."

She said her son was then punched in the ribs several times, and threatened with a knife until he let go of the necklace.

"That's when the security and police were called," she said.

She continued: "He's currently living off the adrenaline rush and shock. He says he's okay but I'm pretty sure he's going to feel the pain later on."

Her son's friend's dad was elsewhere in the centre at the time and dashed to help as soon as he knew what was going on.

The mum said: "I'm just thankful for my son's friend's dad for stepping up and talking to the security and police and making sure he was okay once he got away from them."

A police spokesman said: "Kent Police is investigating following a report of a robbery which was alleged to have happened inside a shop in Greenhithe at around 3.45pm on Sunday, September 4, where a group of people are reported to have stolen a chain from a teenage boy.

"Inquiries are ongoing."

A Bluewater spokesman said: "We are aware of an incident which happened yesterday at one of our brand partner’s sites. As soon as our security team was made aware of the incident we alerted on-site police who are now investigating.

"We work closely with our brand partners and police to make Bluewater a safe place for all our guests – and we’re liaising with authorities regarding this incident."