Saudi Arabia's King Abdullah
Saudi Arabia's King AbdullahReuters

Saudi Arabia said Sunday it has arrested 135 suspects for "terrorism" offences, AFP reported.

The suspects include 26 foreign nationals, mostly from Syria, interior ministry spokesman General Mansour al-Turki said, cited by the official Saudi Press Agency.

The arrests followed "repeated attempts to harm the security and stability of the homeland", Turki said without specifying when they were detained.

40 of the suspects had gone to "zones of conflict, joined extremist groups and trained in the handling of weapons... before returning to the kingdom to destabilize the country," Turki was quoted by AFP as having said.

Numerous others were implicated in the "financing, recruitment, propaganda and manufacture of explosives... in aid of extremist groups".

17 suspects were linked to unrest and armed attacks on security forces in Awamiya, a Shiite-dominated community in Eastern Province just west of Dammam city, which has been a focus for clashes between security forces and minority Shiite protesters.

Turki said that, as well as 16 Syrians, the detained foreign suspects included three from Yemen, an Egyptian, a Lebanese, an Afghan, an Ethiopian, a Bahraini, an Iraqi and a stateless person.

The arrests come as Saudi Arabia, the United Arab Emirates, Jordan and Bahrain take part in airstrikes against the Islamic State (ISIS) terrorist group in Syria.

Even before joining the coalition against ISIS, however, Saudi Arabia has been cracking down on terrorists, both on those within the kingdom as well as on those who leave the country to fight abroad.

In February, the Saudi king decreed jail terms of up to 20 years for belonging to "terrorist groups" and fighting abroad, in another attempt to deter Islamist Saudis from becoming jihadists.

In early March, Saudi Arabia blacklisted the Muslim Brotherhood and two Syrian jihadist groups as terrorist organizations, ordering citizens fighting abroad to return home within 15 days or face imprisonment.

The kingdom has also banned the sale of books by two Islamist authors known to be sympathetic to the Muslim Brotherhood.

In June, Saudi Arabia sentenced 33 suspected Islamist terrorists to up to 30 years in prison.