The European Commission, fresh from a major court victory over Microsoft, launched new antitrust investigations into the software giant on Monday, on suspicion it abused its market dominance.

Brussels will see whether Microsoft broke competition rules to help its Web browser and its Office and Outlook products, after complaints from Norwegian Web browser company Opera and a coalition of technology firms including IBM.

The move goes to the heart of the U.S. company's lucrative near-monopoly over personal computer operating systems, word processing, spreadsheets and office collaboration software.

The Commission is asking if Microsoft used the same tactics to hamper rivals that the European Union's second-highest court found illegal in September, in the culmination of a 6-year antitrust investigation.

The Commission, Europe's top competition regulator, made no new charges against Microsoft but said it "will further investigate the case as a matter of priority."

Microsoft said it would cooperate fully. "We are committed to ensuring that Microsoft is in full compliance with European law and court obligations," it said in a statement.