Nokia filed a patent infringement claim against Apple in October
The legal battle between Finland's Nokia and its US rival Apple has taken a new turn, with Apple countersuing Nokia over alleged patent violations.
The move follows a Nokia lawsuit filed in October accusing iPhone maker Apple of 10 Nokia patent infringements.
Now Apple, in turn, is claiming that the Finnish phone firm is infringing 13 of its technology patents.
"Other companies must compete with us by inventing their own technologies, not just by stealing ours," Apple said.
Apple has not yet revealed which patents are at issue. Nokia was unavailable for comment.
In October, Nokia said it had not been compensated for its technology, and accused Apple of "trying to get a free ride on the back of Nokia's innovation".
The 10 alleged patent infringements by Apple involve wireless data, speech coding, security and encryption.
The breaches applied to all models of the iPhone since its launch in 2007, Nokia added.
Finland's Nokia said that it had agreements with about 40 firms allowing them to use the firm's technology, but that Apple had not signed an agreement.