The European Union opened two antitrust investigations against IBM Corp. on Monday.

The EU accused the U.S. technology giant of abusing its dominant position in the market for mainframe computers.

IBM 3-month chart

One investigation stems from complaints by emulator software vendors T3 and Turbo Hercules.

They allege IBM has tied sales of hardware together with its operating system, shutting out suppliers of competing equipment, which could use emulating software.

Emulating software acts as if it is running on an IBM mainframe whereas it actually runs on cheaper servers.

IBM said in a statement that "there is no merit to the claims."

The other accusation, launched on the EU executive's own initiative, is that IBM discriminates against competing providers of mainframe maintenance services by "restricting or delaying access to spare parts for which IBM is the only source."

Mainframes are powerful computers used by large corporations and governments to store and process critical business information.

It is estimated the vast majority of corporate data worldwide resides on mainframes.

The European Commission estimated worldwide sales of mainframe computers and operating systems in 2009 at the equivalent of $11.4 billion. It put sales in Europe at about $4 billion that year.

IBM shares closed at $128.41 US on the New York Stock Exchange, up three cents.

With files from The Associated Press