The mobile phone of Spanish Prime Minister Pedro Sánchez was tapped using the Pegasus spyware, according to government sources.
The device of Defence Minister Margarita Robles was also the target of "unlawful and external" surveillance, Presidential Minister Félix Bolaños said on Monday.
"These are proven facts of enormous scale" that occurred in mid-2021, he said. It is not yet clear whether there have been more wiretaps and data theft recently, and investigations are ongoing, he said.
More than 2.6 gigabytes of data was stolen from Sánchez's phone, the RTVE TV and the Europa Press news agency learned from government sources.
The prime minister handed in his device after the plot was discovered a few days ago.
The announcement comes some two weeks after it was revealed that dozens of Catalan separatists were allegedly monitored with Pegasus by the Spanish secret service.
PP: 'A coincidence'
Opposition leader Alberto Núñez Feijóo (People's Party, PP) and politicians from other parties called it a "considerable coincidence."
Pegasus was allegedly found in the mobile phones of more than 60 separatist leaders and people close to them, according to the US magazine The New Yorker.
The software developed by the Israeli cyber-arms company NSO Group is capable of reading text messages, tracking calls, collecting passwords, location tracking, among other things.
NSO has repeatedly stressed that Pegasus is only sold to government organizations.
That raises other questions, such as who was then behind the wiretapping of Prime Minister Sanchez.