(In paragraph 2, deletes Reuters stock code for T3, adds company's full name)

BRUSSELS - European Union competition regulators launched two anti-trust investigations against International Business Machines Corp, suspecting it of abusing its dominant position in the mainframe computer market.

One investigation followed complaints by emulator software vendors T3 Technologies Inc and TurboHercules against IBM's practices, and focuses on the U.S. computer group's alleged tying of mainframe hardware to its mainframe operating system.

The second probe, opened on the European Commission's own initiative, concerns alleged discriminatory behavior toward competing suppliers of mainframe maintenance services.

The Commission has concerns that IBM may have engaged in anti-competitive practices with a view to foreclosing the market for maintenance services ... in particular by restricting or delaying access to spare parts for which IBM is the only source, said the Commission on Monday.

The Commission enforces EU competition rules and can fine companies that break them.

IBM rejected the allegations but promised to cooperate fully with the investigation.

IBM is fully entitled to enforce its intellectual property rights and protect the investments we have made in our technologies, the company said in a statement.

It said Microsoft Corp and its other big competitors had inspired the Commission's action.

The accusations made against IBM by TurboHercules and T3 are being driven by some of IBM's largest competitors -- led by Microsoft, it said, adding that in this way the software supplier wanted to cement the dominance of its Wintel servers.

A local Microsoft spokesman had no immediate comment.

IBM shares dipped 0.5 percent in a flat U.S. market by 1356 GMT.

Mainframes are powerful computers which many large companies and government institutions use to store and process critical information. In 2009 customers spent approximately 8.5 billion euros ($11 billion) worldwide and 3 billion in the European Economic Area on new mainframe hardware and operating systems.

The Commission said T3 and TurboHercules had alleged IBM had been illegally tying its mainframe hardware products to its dominant mainframe operating system.

TurboHercules welcomed the Commission's probe.

Hopefully, it will lead to remedies that will allow companies like TurboHercules to compete in the mainframe market, the company said in a statement.

We simply ask that customers be allowed to run their mainframe applications on the hardware of their choice. It is also good news for the Hercules open source community and its 11-year history of innovative development.

(Editing by David Holmes)

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