Nine Americans were detained along with 33 suspects on terrorism charges in Saudi Arabia over the past week, according to local media reports. Four Americans were detained Monday and another five in the following days, the English-language daily Saudi Gazette reported Sunday, citing an anonymous source.

Fourteen Saudis, three Yemenis, two Syrians, an Indonesian, a Filipino, a United Arab Emirates citizen, a Palestinian and a citizen of Kazakhstan were among those detained.

The American embassy in Saudi Arabia is yet to comment on the matter, Reuters reported.

So far this year, jihadis have killed over 50 people in Saudi Arabia. Sunni jihadis attacked a Shiite Muslim mosque in Saudi Arabia's al-Ahsa district in Eastern Province Friday, killing four and injuring 18 others.

On Saturday, Saudi Arabia’s Interior Ministry identified one of the attackers in al-Ahsa as 22-year-old Abdulrahman al-Tuwaijri, a Saudi citizen, who detonated an explosive vest outside the Imam Rida mosque in the Mahasen district of Hofuf.

Apart from the nine Americans arrested this week, four U.S. citizens were detained by Saudi Arabia over the past three months for suspected links to the Islamic State group, also known as ISIS. Saudi Arabia declared ISIS a terrorist outfit in 2014. Supporters of the extremist group have been reportedly responsible for at least two bombings and two mass shootings at Shiite mosques in Saudi Arabia.