Facebook filed a complaint against BlackBerry in a San Francisco federal court, seeking unspecified damages for infringement of six patents, including one around voice messaging technology.

Earlier this year, BlackBerry filed a patent infringement lawsuit against Facebook, claiming the social networking company’s WhatsApp and Instagram apps copied key BlackBerry Messenger technology and features.

The case is part of a strategy announced by BlackBerry CEO John Chen in 2015 to use its patent portfolio to fund the company’s other activities, including its software and enterprise divisions.

At the time, Facebook deputy general counsel Paul Grewal had said: “Having abandoned its efforts to innovate, Blackberry is now looking to tax the innovation of others. We intend to fight”.

Now Facebook is suing BlackBerry for infringing patented technology that improves graphics, video and audio on mobile devices and one that centralises tracking and analysis of GPS data, Bloomberg reported.