Monday night's robbery was "one of the biggest" ever, a spokeswoman for the Antwerp World Diamond Centre said, adding that the diamonds were "rough stones" being transported from Antwerp to Zurich.

The raid saw the gang of thieves hit a security truck from a specialist Brinks security subsidiary as the gems were being loaded onto a Swiss aircraft bound for Zurich.

The AWDC spokeswoman gave no details as to who the shipment belonged to.

According to the AWDC, the global diamond business is worth more than $60 billion each year.