Citizen Lab’s researchers at the University of Toronto published a report on Sunday detailing how NSO Group’s Pegasus spyware infected the mobile phones of 36 journalists, producers, anchors and executives at the media network which has its headquarters in Qatar.

The cybersecurity watchdog attributed the unprecedented attack to Saudi Arabia and the United Arab Emirates.

In confirming the hacking, Tamer Almisshal, an investigative journalist with Al Jazeera Arabic, said a probe was launched after death threats were received on a phone that was used to call ministries in the UAE for a story.