Raiders believed to be brandishing a stun gun threatened security guards outside Yarmouth's busy Tesco Extra store and forced them to hand over a large amount of cash.

Raiders believed to be brandishing a stun gun threatened security guards outside Yarmouth's busy Tesco Extra store and forced them to hand over a large amount of cash.

Detectives were last night investigating possible links with a similar robbery at a Tesco Express store in North Wootton, near King's Lynn, in May when a security van driver was incapacitated by a stun gun.

It is thought the three robbers, who were wearing black balaclavas or face masks, may have been waiting to ambush staff from security firm G4S as they loaded a cash machine in the car park of the out-of-town store at about 6.45pm on Monday.

On this occasion, one of the guards reported hearing an electric cracking noise from a stun gun but no one was harmed.

The raiders, wearing dark tracksuit bottoms and tops, drove off quickly in a black Jeep Cherokee with the registration number V408LUG.

Det Insp Ricky Botwright said: “The raiders said very little apart from demanding the money. The only description we have is that one was 5ft 7in to 5ft 9in and the other two were 5ft 9in to 5ft 10in. They were all of medium build.”

He said they were keen to speak to anyone who witnessed the robbery or may have seen the direction in which the offenders drove off.

“The traffic was very congested along the A12 over Breydon Bridge because of the ongoing road works in Yarmouth so it seems more likely they went from Pasteur Road along the A12 towards Gorleston or turned left into Pasteur Road and then right down Southtown Road,” he said.

“Because the traffic travelling towards Yarmouth on the A12 was in a queue it might have been noticeable to see someone going fast the other way towards Gorleston,” he said.

Det Insp Botwright said there was no set time for delivering the money so it was difficult to say how the machines were targeted as a potential target.

He said, at this stage, there was no confirmation whether the Jeep had been stolen.

Mark Milner, general manager at the Tesco store, said the cash machines were not owned by the company. He said he had been at the store on Monday evening, but the first he knew of the raid was when police contacted him.

A spokesman for G4S confirmed that “the crew of one of our vehicles was attacked during a violent incident in Pasteur Road but the couriers involved were not injured”.

He said: “We are committed to maintaining the safety of our staff and the general public. G4S Cash Services (UK) continues to work closely with trade unions, the police, the government and relevant local authorities to develop initiatives to prevent attacks against those working in the cash-in-transit industry.”

Anyone with information is asked to contact Det Insp Botwright at Yarmouth Police Station on 0845 456 4567 or call Crimestoppers anonymously on 0800 555111.