Yahoo sues Facebook as legal war escalates

Yahoo Inc sued Facebook Inc on Monday over 10 patents that include methods and systems for advertising on the Web, according to a copy of the lawsuit.

The lawsuit, filed in a San Jose, California federal court, marks the first major legal battle among technology giants in social media and a major escalation of patent litigation that has already swept up the smartphone and tablet sectors and high-tech stalwarts such as Apple Inc, Microsoft Corp and Motorola Mobility Holdings Inc.

Yahoo's patent lawsuit follows Facebook's announcement of plans for an initial public offering that could value the company at about $100 billion. A Facebook spokesman did not immediately respond to a request for comment on Monday.

In an emailed statement, Yahoo said it is confident it will prevail.

"Unfortunately, the matter with Facebook remains unresolved and we are compelled to seek redress in federal court," the company said in a statement.

Several social networking companies, including Facebook, have seen an uptick in patent claims asserted against them as they move through the IPO process.

However, most of those lawsuits have been filed by patent aggregators that buy up intellectual property to squeeze value from it via licensing deals and none by a large tech company such as Yahoo.