WhatsApp has accused Israeli spyware company NSO Group of being "deeply involved" in carrying out mobile phone hacks of 1,400 of its users, including senior government officials, journalists and human rights activists.
The allegation was made in a new court filing over the firm's role in the long running hacking case which grabbed global attention following the murder of Saudi Journalist Jamal Khashoggi. Software created by the Israeli spyware firm was used to hack the phone of a member of Khashoggi's inner circle which allowed Saudi security officials to track him.
US whistle-blower Edward Snowden said that if the NSO Group had refused to sell its technology to Saudi Arabia, Khashoggi would still be alive.
A number of human rights defenders and activists in Morocco were also targeted by the Israeli company, according to research by Amnesty International.
The NSO Group has always maintained its innocence insisting that its spyware is purchased by government clients for the purpose of tracking terrorists and criminals and that it had no independent knowledge of how those clients use its spyware.
NSO Group's claim is contradicted by court documents in WhatsApp's lawsuit filed last year against the Israeli firm. While bringing the lawsuit, WhatsApp said in a statement that 100 civil society members had been targeted and called it "an unmistakable pattern of abuse".
New documents seen last week indicate that servers controlled by NSO Group and not its government clients, as alleged by the Israeli firm, were an integral part of how the hacks were executed.
"NSO used a network of computers to monitor and update Pegasus after it was implanted on users' devices," said WhatsApp, "these NSO-controlled computers served as the nerve centre through which NSO controlled its customers' operation and use of Pegasus [software used to hack computers and phones]."
NSO Group is also accused by WhatsApp of gaining "unauthorised access" to its servers by evading the company's security features.
The NSO Group is expected to respond to the court in the coming days.