The European Commission Monday said it has sent formal charges to a number of companies supplying liquid crystal display panels on suspicion that they have operated a cartel.

Dutch electronics maker Royal Philips Electronics NV (PHIA.AE) confirmed it had received cartel charges from the European Commission, alleging price fixing by one of its former units.

Liquid crystal panels are thin, flat monitors used in mobile phones, televisions, computers, digital watches and pocket calculators, the commission said.

The antitrust charges, which were sent out in May, formalize the commission's investigation against the suspected cartel participants. The commission wouldn't name the companies involved.

Philips said the commission alleges that it is "jointly and severally liable for anticompetitive behavior by LG Display" (LPL), formerly known as LG Philips LCD Co., for the period that it held joint control of the company, Philips..

Philips sold its remaining shareholding in LG Display in March 2009. The company said it plans to "vigorously" oppose the commission's charges.

If found guilty the commission can fine the companies involved up to 10% of their annual global sales In reality the fines are usually much smaller than the maximum allowed, but the size of the market affected and the length of the infringement contribute to the final amount.

The European charges mirror closely a LCD cartel case, settled in the U.S. in November 2008.

The U.S. Justice Department fined LG Display $400 million, after the company pleaded guilty to the price fixing. Other companies involved in the U.S. settlement were Sharp Corp. (6753.TO) and Chunghwa Picture Tubes Ltd (2475.TW).

Commenting on the commission's charges, LG Display said it's in the midst of finding the details of the charges, while a Sharp spokeswoman said the company hadn't received any charges from the commission. Samsung C&T Corp.(000830.SE) declined to comment.

-By Peppi Kiviniemi, Dow Jones Newswires; +3227411483; peppi.kiviniemi@dowjones.com