BRUSSELS: Microsoft on Wednesday lodged a formal complaint with the European Union's competition regulator against Google's Motorola Mobility, saying the company's aggressive enforcement of patent rights against rivals breaks competition rules.

The complaint follows a similar step by Apple against Motorola last week. Motorola is in the process of being taken over by Google for $12.5 billion, the biggest acquisition in the Californian company's history.

Apple Inc. and Microsoft Corp. have been hit by legal cases in Europe and the United States, with Motorola claiming that the companies' products are using key patents it owns without permission.

Apple and Microsoft, meanwhile, argue that Motorola is overcharging for the use of these patents, which cover technologies necessary to connect wirelessly to the Internet or stream video online.

"We have taken this step because Motorola is attempting to block sales of Windows PCs, our Xbox game console and other products," Dave Heiner, Microsoft's deputy general counsel, wrote in a blog post.

Officials at Google could not immediately be reached for comment.

The complaints are the latest development in increasingly acrimonious disputes between global technology giants over patents on standardized technologies.

Industry-wide standards play an important role not only in the technology sector. They allow products from different companies to function seamlessly together - different mobile phones or tablet computers connecting via 3-G wireless networks, for example. Under EU competition rules, holders of patents necessary for industry standards are required to let other companies use them for a fair price.

But regulators and companies complain that holders of standardized patents have tried to gain an edge in the market by suing rivals over the use of their patented technologies.

When the European Commission, the EU's competition watchdog, cleared Google Inc.'s takeover of Motorola earlier this month, it indicated concern over Motorola's aggressive patent enforcement. The Justice Department in its clearance of the merger made similar comments.

Separately, the Commission has already launched a formal investigation into Samsung's similar approach to patent protection and has warned that other probes may follow.

Microsoft says Motorola is demanding an unreasonable fee for using its patents, amounting to 2.25 percent of the products' total price. For a $1,000 laptop that would amount to a royalty of $22.50. Microsoft says a group of 29 companies that hold the other 2,300 industry standard patents charge a total of 2 cents for using them.