Saudi Arabia on Sunday said that it has arrested 135 people on charges of terrorism and planning to “destabilize the country.” Of the 135 people detained, 26 are believed to be foreign nationals, the country’s interior ministry said, according to media reports.

At least 40 of the arrested individuals had traveled to “zones of conflict, joined extremist groups and trained in the handling of weapons ... before returning to the kingdom to destabilize the country,” interior ministry spokesperson General Mansour al-Turki said, according to a report by Saudi Press Agency, the official news agency of Saudi Arabia.

Many of those arrested are believed to have links to the Islamic State group and were involved in “financing, recruitment, propaganda and manufacture of explosives ... in aid of extremist groups,” al-Turki reportedly said, adding that 16 of the 26 foreign nationals are Syrians.

Saudi Arabia, along with the United Arab Emirates and Jordan, has been carrying out airstrikes in Syria and Iraq as part of the U.S.-led campaign against ISIS.

Seventeen of the detainees are suspected of being involved in riots in Awamiya -- a village in the oil-rich Eastern Province, which, in recent months, has witnessed several clashes between security forces and minority Shia protesters -- Saudi officials said, according to media reports.

The arrests come amid heightened security in the country following an attack in November on a Shia gathering in the Eastern Province. The attack, which reportedly killed at least seven people, had raised concerns of sectarian violence in the overwhelmingly Sunni country. Saudi officials had blamed Sunni ISIS militants for the attack and accused them of disrupting “the country’s security, stability and peaceful life of citizens,” according to media reports.