Brussels - The European Commission is investigating whether Ryanair's decision to cancel thousands of tickets bought through third-party websites breaches EU rules on air passenger rights.

"I can confirm that we have sent a letter" asking Ryanair to provide additional information, Fabio Pirotta, the EU's transport commission spokesman, told Deutsche Presse-Agentur dpa Wednesday.

The Irish low-cost carrier recently announced that all bookings made on non-Ryanair websites after August 11 would not be honoured, and that passengers would be refunded.

Ryanair argues that so-called "screenscraping" price comparison websites breach its copyright rules, levy unjustified handling charges or do not provide passengers with up to date flight information.

The EU executive is now following up on complaints from consumer groups and wants to find out whether Ryanair is violating the bloc's rules. (dpa)