Irish no-frills airline Ryanair said on Thursday it had canceled its flights for Friday at Belgium's Charleroi Airport due to a planned nationwide strike.

"As a result of a general strike by Belgian trade unions, Brussels Charleroi Airport have confirmed that the airport will be closed on the 28th October," it said in a statement.

"As a result of the airport closure... we have been forced to cancel... flights," it said.

Ryanair allowed travelers to rebook flights free of charge.

Belgium's three biggest unions have called on workers to go on strike for 24 hours on Friday to protest against government plans to raise the early retirement age, part of a package of reforms to prepare for the country's ageing population.

In Brussels, the main Zaventem airport was unable to quantify the extent to which the strike would affect its operations.

But SN Brussels Airlines, the country's main airline, confirmed all of its flights for Friday, even though it admitted to being at the mercy of baggage handlers, caterers and other service providers.

More than 40 km south of Brussels, Charleroi is one of 12 European hubs run by Ryanair, serving 11 routes including Dublin and Rome.