NTP Inc, which last year won a $612.5 million settlement from the maker of Blackberry, has sued four of the top U.S. mobile service providers for infringing eight patents related to wireless e-mail.

The lawsuits, against Verizon Wireless, Sprint Nextel Corp, T-Mobile USA and the mobile unit of AT&T Inc were filed September 7 in the U.S. District Court for the Eastern District of Virginia, according to court documents.

NTP, which is asserting patents related to products, processes and services used for wireless e-mail systems, said it was seeking a jury trial, injunctive relief and monetary damages.

The suits follow a case NTP brought against Treo mobile phone maker Palm Inc in November last year.

The judge in the Palm case granted a stay of the suit in March this year and agreed to strike an NTP complaint alleging misbehavior by Palm at the U.S. Patent and Trademark Office.

Virginia-based NTP is best known for its prolonged patent infringement battle with Research In Motion Ltd, maker of Blackberry, the popular wireless e-mail device.

Officials for AT&T and Verizon Wireless, owned by Verizon Communications Inc and Vodafone Group Plc, declined comment. Sprint and T-Mobile USA, owned by Deutsche Telekom AG, were not immediately available.

(Reporting by Lewis Krauskopf and Sinead Carew)