A University of California patent licensee which has sued some of the biggest US companies is taking on three more -- Facebook Inc, Wal-Mart Stores Inc and the Walt Disney Co.

Eolas Technologies Inc and the Regents of the University of California filed lawsuits on Wednesday over four patents they believe the companies are infringing.

The patents for interactive technology, including hypermedia display and interaction, were issued to the university and licensed to Eolas, a Texas company chaired by Michael Doyle.

The company was founded to help the University of California commercialize patent technology, its website says, including patents Doyle and his team helped develop while he worked at the University of California, San Francisco.

A University of California spokesman said it considered the patents public assets and should be paid a fair value when a third party exploits that university asset for profit.

A Facebook spokesman said the company believed the lawsuit was without hermit. We will fight it vigorously, he said.

A Wal-Mart spokesman said the world's largest retailer respects the intellectual property rights of others. We take these allegations seriously and are looking into the matter.

Disney did not immediately respond to requests for comment.

A spokesman and several lawyers for Eolas did not immediately respond to requests for comment.

Two of the patents cited in the latest lawsuits were declared invalid in February by a Texas jury in a separate lawsuit. That action targeted Amazon Inc, Google Inc, Yahoo Inc and others. The process by which Eolas could launch new lawsuits concerning those same patents was unclear.