Masked raiders have burgled five Sainsbury's supermarkets in Sussex in less than a month.

Police are linking the break-ins with others in Kent and south-east London.

The gang, described as "very professional", have escaped with thousands of pounds.

One insider said: "They found a weak-link in Sainsbury's security and have been exploiting it for weeks.

"Sainsbury's is now tightening its systems."

The gang break into branches, smash open cash registers and escape with tills, floats and Nectar loyalty vouchers.

Some night staff who have challenged them, backed off when they were threatened with violence.

The latest raid happened at Sainsbury's in The Drove, Newhaven, at 1.20am last Saturday.

A Sainsbury's spokeswoman confirmed there had been similar incidents at other stores in its chain within the last four to six weeks.

Raids in Sussex began on July 22 ,when three of the supermarket's branches were hit.

They were at the giratory in Lewes Road in Brighton, Hampden Park in Eastbourne and Hangleton in Hove.

The Lyons Farm branch in Worthing was raided on August 3.

Police appealed for witnesses or anyone with information to call 0845 6070999.