Rights groups earlier reported arrests of at least 11 people last month, mostly identified as women campaigners for the right to drive and to end the conservative Islamic country´s male guardianship system.
Without naming anyone, the public prosecutor´s office said the number of detainees stood at 17, adding that eight of them had been “temporarily released” until the investigation is completed.
Nine suspects, including four women, remain in custody after they “confessed” to a slew of charges such as suspicious contact with “hostile” organisations and recruiting people in sensitive government positions, it said in a statement released by the Saudi Press Agency.
The statement accused the detainees of “coordinated activity undermining the security and stability of the kingdom”.
Previous reports in state-backed media branded some of the detainees traitors and “agents of embassies”.
Campaigners have dismissed the reports as a “smear” campaign.
The crackdown has also sparked a torrent of global criticism, casting a shadow on the kingdom´s much-publicised liberalisation push launched by powerful Crown Prince Mohammed bin Salman.
The self-styled reformer has sought to break with long-held restrictions on women and the mixing of the genders, with the decades-old driving ban on women slated to end June 24.
The European Parliament last week approved a resolution calling for the unconditional release of the detained activists and other human rights defenders, while urging a more vocal response from EU nations.
“The Saudi Arabian authorities´ endless harassment of women´s rights activists is entirely unjustifiable, and the world must not remain silent on the repression of human rights defenders in the country,” Samah Hadid, Amnesty International´s Middle East director of campaigns, said last week.
“Saudi Arabia´s allies — in particular the US, UK and France — must push Saudi Arabian authorities to end their targeted repression of human rights activists in the country.”