Saudi Arabia said Sunday it has arrested 135 suspects for "terrorism" offences, after the kingdom's participation in air strikes against Islamic State group extremists raised concerns about possible retaliation.
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.
Forty 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 destabilise the country," Turki said.
Numerous others were implicated in the "financing, recruitment, propaganda and manufacture of explosives... in aid of extremist groups".
Seventeen 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.
Awamiya 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 US-led air strikes against the IS extremist group in Syria.
As the "epicentre of Islam," Saudi Arabia is the primary target of IS and its efforts to restore an Islamic caliphate, two Saudi analysts, Nawaf Obaid and Saud al-Sarhan, wrote in a September commentary published by The New York Times.
- Westerners attacked -
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Last week an IS-linked media group released a video claiming to show the shooting in Riyadh of a Danish national by its "supporters", the US-based SITE Intelligence Group said.
Denmark has confirmed that one of its citizens was shot and wounded in the Saudi capital on November 22.
The video carries an audio recording, allegedly of IS leader Abu Bakr al-Baghdadi, saying that Saudi rulers will see "no more security or rest".
A week after the Dane was shot, someone stabbed and wounded a Canadian while he shopped at a mall in Dhahran on Saudi Arabia's Gulf coast.
Police arrested a Saudi suspect.
In October, a Saudi-American former employee of a US defence contractor shot dead an American colleague and wounded another in Riyadh.
The suspect had recently been fired, officials said.
That was the first deadly strike against Westerners in Saudi Arabia since several were killed in a wave of Al-Qaeda violence between 2003 and 2007.
Both Canada and Denmark are among the Western states taking part in an aerial bombing campaign against IS in Iraq.
A Saudi government adviser, who declined to be named, told AFP the latest arrests demonstrate the interior ministry is "in control" of the threat posed by IS inside the kingdom.
In November, Saudi Arabia blamed IS-linked suspects for the killing of seven Shiites, including children, in Eastern Province.
Security forces in the Sunni-dominated kingdom arrested 73 Saudis and four foreigners in connection with that attack, the interior ministry announced earlier.
"Saudi certainly has a problem with ISIS (IS), and it seems there is now a trend to carry out attacks in the Gulf, including in Saudi," said Toby Matthiesen, a research fellow at the University of Cambridge.
The interior ministry called on citizens to remain vigilant.