Finland's Nokia Corp. has sued Apple Inc. in Germanyand the United States, alleging that Apple products infringe a number of Nokia patents, according to a statement issued Wednesday on Nokia's official website.

The statement said, Nokia, a Finnish multinational communications and information technology company and once the world's top mobile phone maker, signed a license agreement covering several patents owned by the company with Apple in 2011.

"Through our sustained investment in research and development, Nokia has created or contributed to many of the fundamental technologies used in today's mobile devices, including Apple products," Ilkka Rahnasto, head of Patent Business of Nokia, said in the statement.

However, Apple refused to pay for other patents while using them, which are not covered in the licensing agreement, said the statement.

"After several years of negotiations trying to reach agreement to cover Apple's use of these patents, we are now taking action to defend our rights," said Rahnasto.

Nokia has filed the complaints with three courts in Germany and a district court in southern U.S. state of Texas.

After selling its handset business, Nokia has focused on networking. Therefore, patents have become a significant source of the company's income.

In the third quarter, Nokia's technology unit, which licenses its patents, generated about 40 percent of the company's total adjusted operating profit, according to financial website Bloomberg.

"Apple has regularly fought to keep royalty rates low, whereas Nokia is interested in getting as much value from its intellectual property as possible," Bloomberg analyst Matt Larson said.

According to Bloomberg, Apple has replied with an e-mailed statement, which said "unfortunately, Nokia has refused to license their patents on a fair basis and is now using the tactics of a patent troll to attempt to extort money from Apple by applying a royalty rate to Apple's own inventions they had nothing to do with."