Police were today hunting a gang of armed raiders who stole thousands of pounds from a Post Office van waiting outside a supermarket.

Three men, wearing balaclavas, lay in wait as the van arrived at the Asda store at The Crumbles, on the outskirts of Eastbourne. They watched as the driver got out, then they burst through a side door into the store's post office.

The delivery driver was threatened by the men, one brandishing a gun, who demanded cash from post office staff.

When the attempt failed they ran outside and emptied boxes containing a "substantial amount" of cash from the van.

The trio sped away in a maroon car.

A Vauxhall Cavalier, registration K140 ATX, was later found abandoned at the Martello Inn, Langney.

The car, which had been reported stolen, has been seized by police and is being examined by forensic experts for traces of evidence.

Detectives are appealing for shoppers who witnessed the raid, at 11.30am yesterday, to contact them.

Detective Sergeant Nick Porter said: "The Cavalier was stolen from East Dean Road, Eastbourne, sometime between 5.30pm on Sunday and 1pm yesterday."

An ambulance was called to the scene to treat people for shock.

Police remained in the store talking to shoppers who had been using a shortcut near the side entrance where the robbery took place.

Staff at the post office declined to comment on the raid.

The armed robbery comes after two incidents at One Stop convenience shops in nearby villages.

In June, two men threatened security staff with knives and stole money destined for a cash point in Stone Cross.

On July 7 a man terrorised staff by waving a gun and demanding cash. A man has since been arrested and charged.

Anyone with information about yesterday's robbery is asked to contact Eastbourne police on 0845 6070999.