KLM staff were threatened in the raid

An armed gang disguised as airport workers entered a secured area and hijacked a lorry about to load the valuables onto a flight to Antwerp.

Security staff from the airline, KLM, were threatened but no-one was hurt.

The empty lorry was later recovered in a nearby town. Police are searching the vehicle for evidence.

World's biggest robberies Feb 2005: �52m diamond and jewel theft at Amsterdam airport, Netherlands Feb 2003: �65m diamond robbery in Antwerp, Belgium 1994: �29m gems raid in Cannes, France Jul 1987: �60m robbery at Knightsbridge safety deposit centre, London Nov 1983: �26m Brinks Mat robbery at Heathrow, London Jan 1976: �22m robbery at British Bank of the Middle East in Beirut, Lebanon Apr 1945: Reichsbank in Berlin, Germany looted. Estimated �2.5bn stolen. Source: Guinness World Records

Correspondents say it is the second time a KLM flight has been robbed in six months.

The gems were on their way to a flight bound for Antwerp, Europe's diamond capital, when the robbers struck.

Nobody was injured in the raid, KLM said.

Schiphol police told the BBC that the robbery happened just before the "high value goods" were going to be loaded onto the plane and that there were plenty of witnesses.