BRUSSELS, Nov 6 (Reuters) - The European Commission on

Thursday said it had opened an antitrust investigation against

stock exchange companies Deutsche Boerse and Nasdaq

.

The Commission said it suspected the companies of breaking

EU competition rules in the sector for listing, trading and

clearing of financial derivatives.

"Deutsche Boerse and Nasdaq entities may have entered into

agreements or concerted practices not to compete in the European

Economic Area," it said. "In addition, the entities may have

allocated demand, coordinated prices and exchanged commercially

sensitive information."

(Reporting by Bart Meijer, editing by Inti Landauro)