Diamonds have been synonymous with Antwerp for 600 years

Besides the gems, the raiders also stole security documents designed to prove the diamonds' authenticity.

The raid is being described as the most daring diamond heist in history - 123 out of 160 safes at Antwerp's high security diamond centre were burgled.

Simon Gilbert, a spokesman for De Beers, the world's biggest producer of rough diamonds explained how the diamond area was a series of streets with extremely high security.

"There are police at the pedestrianised entries and diamonds are moved around by armed couriers," he said.

"Security is paramount in the area due to the nature of the material we deal in," he added.

While officials are refusing to speculate, many observers assume the raid required help from within the trade.

Dome raid thwarted

True to the town's style, the burglars' employed discretion - unlike the attempted raid on London's Millennium Dome in 2000, when armed robbers used a JCB digger and high-powered drills, in a raid thwarted by police.

The diamond trade has come under close scrutiny

This time the burglars avoided security cameras, and also took certificates which state gems' origin and value.

Recent years, and the identification of so-called "blood diamonds" used to fund wars, have brought new efforts to keep track on the diamond trade.

But Peter Lilley, an expert on money laundering, said that nonetheless the diamond trade has become a favourite for money launderers, who have moved away from exploiting the banking sector.

Reputation dented

This heist will damage Antwerp's reputation - damage that traders in other diamond centres will be keen to exploit.

Antwerp has been a diamond centre for 600 years and it is estimated that 80% of the world's diamonds pass through Antwerp at some stage.

Rival diamond trade centres include New York, Tel Aviv and Mumbai in India.