Finnish cell phone maker Nokia said Friday that it has extended its patent-infringement claims against Apple to include the new iPad.
The latest complaint, filed in U.S. District Court in Madison, Wis., follows other lawsuits by Nokia claiming that a broad swath of Apple products violate Nokia patents. Nokia says the disputed technologies help reduce the size and cost of electronic gadgets. Apple had already responded with its own infringement claims against Nokia.
Lawsuits over patent rights are common in the technology industry. They can take years to resolve and often end with some kind of licensing agreement.
Apple has also sued Taiwan's HTC Corp., one of the leading producers of cell phones that run on Google's Android software, a potential challenger to Apple's popular iPhone. Apple says HTC's Android phones violate iPhone patents.
The legal disputes come amid increasing competition in the fast-growing market for smartphones. Tech companies are scrambling to win over the growing number of consumers buying cell phones that come with e-mail, Web surfing and scores of apps for checking the weather, updating Facebook and other tasks.
Nokia is the world's biggest cell phone maker, though it is more dominant in Asia and Europe. In the U.S., it faces intense competition from the iPhone and Research in Motion's BlackBerrys.
Nokia's latest lawsuit targets the iPhone and the iPad 3G, the version of the device that can connect to the Web using cell phone networks. Nokia said the gadgets infringe on five patents related to technology that makes voice and data communications more efficient, which allows the devices to be more compact.
"We have taken this step to protect the results of our pioneering development and to put an end to continued unlawful use of Nokia's innovation," Nokia executive Paul Melin said in a statement.
Apple spokesman Steve Dowling declined to comment on the new case but said the company had already filed a countersuit in December to earlier claims by Nokia.
Apple claims Nokia is infringing on 13 of its patents, saying the company chose to "copy the iPhone" in order to recapture its share of the high-end phone market.