The detainees also stand accused of being part of group which shot and killed eight worshippers in the eastern Saudi village of al-Ahsa, and a separate attack in May when a male suicide bomber dressed in a burqa killed four people in a Shia mosque.

The latest arrests come after the Interior Ministry said it thwarted a suicide bomb attack on a mosque in the east of the kingdom that is capable of holding some 3,000 worshippers, as well as a string of attacks on other mosques and official buildings.

Saudi Arabia toughened its stance on Isis last year, by launching air-strikes in Iraq and Syria as part of a US-led coalition against the group’s so called Islamic State caliphate spanning swathes of Iraq and Syria, and by branding it a terrorist organisation.

Theodore Karasik, a Dubai-based geopolitical analyst, told theAssociated Pressthat arrests are part of attempts by the authorities to reassure the hard-line Sunni country’s Shia minority, who long have complained of discrimination in the kingdom.

“It sends a message that the Ministry of Interior is not losing a grip and wraps up the potential nodes of Daesh [Isis] recruits in the kingdom,” he said, using a derogatory Arabic term for Isis which also aligns itself to Sunni Islam.

It is yet unclear how the authorities will deal with the suspects, in a nation that is notorious for its liberal use of executions against prisoners.

Additional reporting by AP