About 50 flights from Brussels Airport, which reopened this month after a deadly bomb attack, were cancelled on Wednesday as a strike among air traffic controllers entered a second day.

Brussels Airport, one of Europe's busiest, reopened on April 3 with limited capacity, restricted by tight security and temporary structures erected after bombs destroyed the departure hall on March 22.

Labour leaders had asked staff to call in sick on Tuesday due to disagreements over a proposed dispute settlement, including a rise in the minimum retirement age.

A spokesman for air traffic authority Belgocontrol said some workers had again called in sick on Wednesday but capacity was increased to 20 landings or take-offs per hour from 15 earlier in the day.

"We'll go to 25 later in the day," the spokesman said.

A spokeswoman for Brussels Airport said some 50 flights had been cancelled until midday on Wednesday, out of about 400 scheduled flights.

Brussels Airlines, the largest operator at Brussels Airport said it had to cancel flights and was giving priority to intercontinental destinations and connections to busy European hubs.

Flights into Belgium's second largest passenger airport in Charleroi, a low-cost airline hub, had not been affected on Wednesday, a spokesman said.

The strike had been severely criticised by Iata, the world airlines' main trade association, which called it a "kick in the teeth" for airlines and airport staff. - Reuters