The European Commission has opened an investigation into Ryanair's use of a terminal at the airport in Tampere, Finland, a Commission spokesman said yesterday.

The terminal, which is only being used by Ryanair, is a cargo hall that has been turned into a no-frills passenger hall that costs less to maintain, meaning Ryanair pays less than other airlines for operating at the airport.

The spokesman said that the probe followed a complaint against Ryanair from an unidentified source.

"We have already had some fruitful discussions with the civil aviation authority, which is the owner of that airport, and we are conducting an investigation now," the spokesman said.

Ryanair said in a statement the deal between it and Tampere airport is legal and supports competition.

"It is open to all airlines that fulfill the same passenger traffic commitments that Ryanair currently does at Tampere airport," Ryanair said.

The head of Finland's Civil Aviation Authority (CAA), Samuli Haapasalo, said he thinks the Ryanair-Tampere case "is rather clear".

"We have turned a cargo hall into a passenger terminal and prepared it so that the level of services there is not as high as in our other terminals, meaning the prices we are offering there are also lower," Mr Haapasalo said.

"But, that terminal is open to all our clients, not only Ryanair. We have informed 50-60 other airliners about this terminal for more than a year ago, but only Ryanair took the offer," said Mr Haapasalo.

"I feel in this case we are supporting the competition and initiative for all airliners, and we are still open for new customers," he added.