The revelation is likely to reignite a tense row between Madrid and pro-independence activists in one of the country’s wealthiest regions, which led to a major political crisis in 2017.

An estimated 50 percent of the population of the autonomous Spanish region of Catalonia wishes to secede from Spain. However, Madrid refused to recognize the legitimacy of an independence referendum organized by secessionist activists in 2017. The stalemate led to massive protests throughout the country, which were marred by violence and thousands of arrests, as Spain faced its deepest political crisis since the 1970s. In response to the protests, the central government suspended Catalonia’s autonomous status and arrested many of the independent movement’s leaders. Many of them have been given lengthy jail terms, while others remain abroad and are wanted by the Spanish government for promoting insurrection.

On Monday, British newspaper The Guardian and Spanish newspaper El País revealed the results of a joint investigation, according to which the smartphones of senior Catalan pro-independence politicians were targeted by hackers in 2019, and possibly even earlier. Among them was Roger Torrent, who serves as the speaker of the Parliament of Catalonia. The newspapers said he had been alerted to the hacking by cybersecurity employees of WhatsApp, a Facebook-owned company whose application was allegedly used by the hackers to take control of Torrent’s phone.

The software that was allegedly used to hack the Catalan politicians’ phones was Pegasus. It was built by NSO Group, an Israeli software development company that specializes in surveillance technologies. According to WhatsApp, which sued NSO Group in 2019, NSO Group specifically developed the Pegasus hacking platform to enable its users to exploit flaws in WhatsApp’s servers and to gain access to the telephone devices of targeted individuals. Pegasus allegedly allows its users to covertly operate a compromised phone’s camera and microphone.

Several human rights groups and university researchers have alleged that Pegasus is being used by authoritarian regimes around the world to spy on journalists, political activists and the lawyers who defend them. But NSO Group, whose clientele consists exclusively of government agencies, denies any wrongdoing and claims its products are designed to help governments around the world spy on terrorists and criminals.

The latest allegations point to the government of Spain as the culprit of the espionage attacks against Catalan independence activists. If proven to be true, they would mark the first time that a member of the European Union has been associated with the controversial Pegasus software. Speaking on Monday, Torrent said the revelations “conclusively prove” what “many of us already knew and have been denouncing for a long time”, namely that “espionage against political opponents is practiced in Spain”.

Spanish authorities, including a spokesman from the Office of the Prime Minister, have denied being behind the espionage attacks. Spain’s primary intelligence service, the National Intelligence Center, issued a statement on Monday saying that it operates “in full accordance with the legal system” and under the supervision of the Supreme Court of Spain.