Mobile phone maker Nokia has filed a new U.S. lawsuit accusing Apple of patent infringement, according to court documents, escalating the legal battle between the companies.The lawsuit, filed last week in the U.S. District Court for the District of Delaware, follows another suit Nokia brought against Apple in October. That suit alleged that Apple infringed 10 Nokia patents by using certain wireless technologies in the iPhone. Apple filed a countersuit last month accusing Nokia of infringing 13 Apple patents. The new suit lists seven patents Nokia alleges Apple has violated in versions of the iPhone, the iPod, the MacBook and in other products. It requests an injunction blocking Apple from further infringement and seeks related damages from Apple.An Apple spokeswoman declined to comment. Nokia did not immediately reply to a request for comment.The latest suit was filed on the same day Nokia made similar allegations in a complaint with the U.S. International Trade Commission. Nokia and Apple have exchanged harsh words over the allegations. "Other companies must compete with us by inventing their own technologies, not just by stealing ours," Apple general counsel and senior vice president Bruce Sewell said in a statement when the company filed its suit. Paul Melin, general manager of patent licensing at Nokia, said in a statement last week that his company's earlier suit was "about Apple's attempt to free-ride on the back of Nokia investment in wireless standards."