(Adds Microsoft reaction in paragraphs 6, 7)
BRUSSELS Dec 13 (Reuters) - A small Norwegian maker of Web browsers, backed by an industry coalition, has filed the first complaint against Microsoft to the European Commission since the software giant lost a landmark antitrust case earlier this year.
Opera Software said it has complained that Microsoft Corp (MSFT.O) illegally ties its Web browser, Internet Explorer, to its dominant Windows operating system.
Microsoft is also "hindering interoperability by not following accepted Web standards", the company said.
Both make it difficult for Opera to compete, it said.
Commission spokesman Jonathan Todd confirmed that the EU executive had received the complaint, which comes after a Sept. 17 EU Court of First Instance ruling that upheld a 2004 European Commission decision against the company on antitrust grounds. Todd said the complaint would be studied carefully.
A Microsoft spokesman said Internet Explorer had been part of Windows for more than 10 years and supported many Web standards.
"We will of course cooperate with any inquiries into these issues, but we believe the inclusion of the browser into the operating system benefits consumers, and that consumers and PC manufacturers already are free to choose any browsers they wish," the spokesman said.,
Opera is a member of the European Committee for Interoperable Systems (ECIS), a long-time opponent of Microsoft, and ECIS issued a statement critical of the software giant.
"By tying its Internet Explorer product to its monopoly Windows operating system and refusing to faithfully implement industry accepted open standards, Microsoft deprives consumers of a real choice in Internet browsers," ECIS lawyer Thomas Vinje said in the statement.
Opera's complaint echoes a U.S. case from 1998, in which the U.S. Justice Department won a major judgment against Microsoft for competing illegally against another browser, Netscape.
Opera asked the Commission to force Microsoft to unbundle Internet Explorer. It also asked the Commission to require Microsoft to follow "fundamental and open Web standards". (Reporting by David Lawsky; Editing by Paul Bolding/Quentin Bryar)