Research In Motion, the maker of the Blackberry handset said on Monday it's suing Motorola, claiming that the company infringed some of its patents and over exorbitant licensing fees Motorola charges while refusing to acknowledge or pay royalties for certain patents held by RIM.

The civil action, filed on Friday in U.S. District Court for the Northern District of Texas, alleges that Motorola infringed on a number of patents held by RIM.

Having suffered losses in the marketplace, Motorola has now resorted to demanding exorbitant royalties from its competitor, RIM, for patents that Motorola claims are essential to various standards for mobile wireless telecommunications, said Research In Motion Limited in its court filing.

RIM says Motorola charges too much for a number of wireless technologies that have become industry standards. These services include a technology that enables the use of Wi-Fi on a mobile device.

At the same time, Motorola is refusing to acknowledge or pay royalties for certain patents held by RIM, the Canadian BlackBerry-maker said. This includes a patent for a mobile device with a keyboard optimized for use with the thumbs.

Motorola's strong R&D [research and development] and intellectual property are critical to our business. Motorola believes in the value of its IP and will move aggressively to protect that value on behalf of our customers, partners and shareholders, Motorola said in a statement.

None of the allegations have been proved in court.

As of December, RIM had 12 million BlackBerry subscribers world-wide, up from seven million in December 2006. The company released its first BlackBerry handheld in 1999 and has been broadening its mainstay enterprise market into the consumer sector with sleeker and trendier handsets that offer a range of services in addition to e-mail.