Nine Americans are amongst the 33 people who have been detained in Saudi Arabia on terrorism charges in the past week.
Citing an unnamed source, the Saudi Gazette reported that four Americans were detained on 25 January, and another five in the following days.
14 Saudis, three Yemenis, two Syrians, and Indonesian, a Filipino, a United Arab Emirates citizen, a Palestinian and a Kazakhstani were the other detainees.
The Saudi Interior Ministry did not provide Reuters with specific details of the charges against the Americans, and the American embassy in Riyadh did not immediately respond to comment requests.
In 2014, Saudi Arabia declared Isis a terrorist organisation, and has detained hundreds of its supporters.
Isis has staged a string of attacks in the Kingdom since gaining power in neighbouring countries, including a number of bomb and gun attacks at mosques around the country.
On 29 January, an attack at a Shia Muslim mosque in the eastern Al-Ahsa region killed four people and injured 18. The allegiances of the attackers, one of whom was killed after blowing himself up and another who was captured, has not yet been announced.
However, the dead attacker has been identified as 22-year-old Abdulrahman al-Tuwaijri, a Saudi citizen.
