Shopkeepers were warned to be on guard after armed robbers struck for the fifth time in six days.

Police said the raiders, dubbed the Benson and Hedges gang because of the brand of cigarettes they steal, are becoming bolder and may resort to violence.

The pair's latest target in Brighton was Thresher's off-licence in Western Road.

Detectives were telling the media about the previous four raids yesterday as the thieves were carrying out their fifth.

They burst into the shop at 4.45pm and threatened the cashiers with a five-inch knife.

They made staff open the till and a safe and fled with cash, phone cards and cigarettes.

The robbers drove off in an F-registered blue Astra stolen 30 minutes earlier from the car park of Gala Bingo in Eastern Road, Brighton.

The vehicle was later abandoned in St John's Road, Brighton.

Detective Constable Barry Sutherden, of Brighton and Hove CID, said: "The pair are becoming more daring and we are becoming more concerned."

He appealed to anyone who witnessed the raid or the theft or dumping of the Astra to come forward.

The robbers struck at a BP service station in Kingsway, Hove, at 11pm on Sunday when they threatened staff with a knife and made off with the contents of the till.

Their first robbery was last Wednesday at Threshers in Holland Road, Hove, just before 6.30pm. They threatened staff with a screwdriver and fled with cash and cigarettes.

A similar robbery came the following night at Threshers in Queen's Park Road, Brighton, and the gang's third was at the Asda supermarket in Brighton Marina in the early hours of Saturday.

Police declined to say how much was taken at the Asda store but it is believed to be more than £1,000.

The robbers are in their late teens or early 20s, slim, with Northern accents.