The European Commission Monday opened two new antitrust investigations against Microsoft Corp. over complaints that the company is continuing to abuse its dominant position through its Office software and its Internet Explorer browser The commission is investigating whether Microsoft has illegally refused to disclose "interoperability information" across a range of products, including its Office suite, hindering rivals from creating compatible products.

The case results from a complaint brought forward by some of Microsoft's main rivals, including International Business Machines Corp. and Oracle Corp. of the U.S., banded together as the European Committee for Interoperable Systems, or ECIS.

The second area in which the commission is investigating Microsoft, is in the field of browsers, where Microsoft is accused of tying its Internet browser Explorer into the Windows operating system in ways that keep competitors from entering the market. The probe follows a complaint by competing browser vendor Opera Software ASA, based in Norway.

The Opera complaint follows the logic of the EU's successful antitrust pursuit of Microsoft. European regulators charged Microsoft with illegally bundling its Media Player software with Windows to box out rivals. They also said Microsoft withheld specifications needed for competitors to make their machines work with Windows. Microsoft received a record fine that could amount to billions of euros.

In September, the software giant said it wouldn't appeal a ruling by a top European Union court that backed sweeping powers for EU antitrust regulators to tackle the abuse of a monopoly position by technology companies. Microsoft's decision not to appeal left that ruling as settled law.