Irish low-cost carrier Ryanair on Friday announced the closure of a recently opened base in Copenhagen to avoid a strike by Danish unions, but said it would continue to fly from the airport.

Europe's largest budget airline has courted controversy by refusing to enter into a collective bargaining agreement with a Danish union for pilots and cabin crew.

On March 18 its first flight from Copenhagen was grounded for three hours by a group of demonstrators, and last week a Danish court cleared the way for a sympathy strike by other unions, potentially affecting services such as luggage handling and fuel deliveries.

"Ryanair will continue to grow in Copenhagen Airport. All of these flights will now take place on aircraft based outside of Denmark," spokesman Eddie Wilson said in a statement.

"The Danish (labour) model cannot work in the airline industry where the aircraft and jobs are mobile," he added.

Ryanair's only Copenhagen-based aircraft would be stationed in Kaunas in Lithuania starting Tuesday, the company said.

In May, Copenhagen mayor Frank Jensen said city employees were banned from using the airline, citing his administration's policy on companies that engage in "social dumping".

It was unclear if Ryanair would continue to base aircraft at the Billund and Aarhus airports in western Denmark, where the Danish Confederation of Trade Unions (LO) has said a strike will begin on July 23.

Ryanair has operated for years without any conflicts at the two airports, where it faces less competition and staff have fewer job opportunities.

In October a French court found Ryanair guilty of paying workers under Irish contracts to save money on payroll and other taxes and ordered it to pay 8.1 million euros ($9.1 million) in damages and fined it 200,000 euros for breaching French labour law.

The airline had argued that it did not have a permanent base at Marseille-Marignane airport, but prosecutors said its claim was not credible since it had offices there and workers were living locally.