Hundreds of suspected members of the Islamic State group have been arrested in Sunni-dominated Saudi Arabia in recent weeks, the country’s Interior Ministry announced Saturday. The detainees include people suspected in attacks on Saudi security patrols and the recent bombing of a Shiite mosque.

During the recent sweeps, 431 suspects were arrested, most of them Saudi nationals, “as well as participants holding other nationalities, including Yemeni, Egyptian, Syrian, Jordanian, Algerian, Nigerian, Chadian and unidentified others,” the official Saudi Press Agency reported. Officials said at least 37 civilians or members of security forces were killed and 130 of them were injured in these operations, while six suspects were also slain.

At least four terrorist cells were identified by Saudi authorities, including one charged with making suicide-bombing belts and another detailed to survey a unnamed foreign diplomatic mission.

Officials also thwarted seven planned attacks on mosques in the country’s capital Riyadh and in its Eastern Province, where many oil installations are located, Gen. Mansour Al Turki, an Interior Ministry representative, said at a press conference, according to Al Arabiya News. He said Saudi security forces in June blocked a planned attack on a mosque that holds 3,000 people. He also blamed some of the suspects for the fatal shooting of eight worshippers in the town of al-Ahsa in November and the killing of three security officers in two separate shootings in Riyadh this year.

Saudi Arabia has been on high alert since a suicide bombing May 22 killed 21 worshippers at a Shiite mosque in the eastern town of al-Qadeeh. It was the deadliest terrorist attack in the kingdom since the May 2004 attacks by al Qaeda militants on a foreign residential compound in Al-Khobar that killed 22 foreigners. Days after the al-Qadeeh attack, Islamic State group affiliates called for increased attacks in Saudi Arabia and urged young Saudis to join their cause.

The extremist group and other militant organizations have long viewed the Saudi ruling family as both illegitimate and pro-Western.