Facebook-owned WhatsApp filed a lawsuit against Israel’s NSO Group on Tuesday in California.

The US-based platform alleges that the Israeli company staged cyber-attacks in April and May in order to infect 1,400 mobile phones. The motive was to facilitate illegal surveillance over the private accounts of journalists, human rights activists, political dissidents, and diplomats in Bahrain, the United Arab Emirates, and Mexico.

The NSO Group is a software developer for surveillance but disputes WhatsApp allegations and promised to contest them in court. “The sole purpose of NSO is to provide technology to licensed government intelligence and law enforcement agencies to help them fight terrorism and serious crime,” the company said in a statement to BBC.

WhatsApp promotes itself as a “secure” communications app because messages are end-to-end encrypted. WhatsApp alleges that the NSO Group reverse-developed a system that emulates the platforms’ network traffic to transmit malware that could take over the mobile devices. The NSO group has been implicated in the information that facilitated the murder of the Washington Post Journalist Jamal Khashoggi in 2018, the German public broadcaster DW reports.