San Francisco: A US jury has found Microsoft guilty of infringing Alcatel-Lucent patents and ordered the software giant to pay the French-US firm $1.5 billion.

Microsoft denied the charge, saying, "We contend that there was no infringement of any kind and that we have paid the appropriate license fees for any technology that is used in our products," Microsoft said in the wake of the verdict.

Microsoft's general counsel Tom Burt issued a written statement yesterday, saying, "We think this verdict is completely unsupported by the law or the facts. We will seek relief from the trial court, and if necessary appeal."

Before it merged with Alcatel SA of France in 2006, Lucent Technologies had filed a US federal lawsuit in 2003 claiming Microsoft partners, including computer makers Dell and Gateway, used Windows software that infringed its patented technology.

The case is part of a broader intellectual property dispute between Microsoft and Alcatel-Lucent. A total of 15 patents were in dispute when the litigation began. Two of the claims were dismissed and the remaining patents were divided into six groups, each the subject of separate jury trials in San Diego.

The jury trial that ended in US district court in the Southern California city of San Diego centred on MP3 audio technology used in the Windows Media Player software.

Alcatel-Lucent argued in court that technology used to encode and decode digital audio files in Media Player infringed on its patents.