Belgocontrol said controllers had stopped work at 1400 CET (1200 GMT, 8 pm S'pore time), but it gave no explanation for the strike.

The spontaneous action, announced late on Monday, is due to last for 24 hours. Belgocontrol said it was in talks with those involved to try to bring end it sooner.

A spokesman for Brussels airport said around 50 flights to and from the airport had already been cancelled due to the strike. Strike is resulting in backlog at BRU airport for export shipments, as well as delays for incoming freight.

Belgian media said the strike was related to some staff being moved from the city of Charleroi to Brussels.

Sources: Reuters, CNN, The Straits Times, BDP International