Saudi Arabia announced Saturday it has broken up an Islamic State group-linked network and made more than 430 arrests, foiling new attacks on Shiite mosques and a diplomatic mission.
The IS jihadist group has claimed several deadly attacks in the Sunni-dominated kingdom.
Authorities have "managed over the past few weeks to destroy an organisation, made of a cluster of cells, which is linked to the terrorist Daesh organisation," the interior ministry announced, using the Arabic acronym for IS.
The alleged members were engaged in a "plot managed from areas of unrest abroad, with the aim of sowing sectarian sedition and spreading chaos", the ministry said.
The cells were involved in several attacks and plots, including deadly suicide bombings of Shiite mosques in the kingdom's Eastern Province, it said.
The ministry said 37 people were killed during the arrests, including security personnel and civilians, and 120 were wounded. Six "terrorists" were also killed in the operations.
It said authorities had foiled bomb attacks plotted during the Muslim fasting month of Ramadan, including on a mosque used by security forces in Riyadh and other Shiite mosques in the Eastern Province.
The group also plotted to attack a diplomatic mission, the statement said without elaborating.
Among the 431 suspects so far rounded up, mostly Saudis, were 144 people accused of supporting the network by "spreading the deviant ideology on the Internet and recruiting new members".
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The ministry said 97 of those arrested were linked to a cell busted earlier and to a November attack on a Shiite mosque in the town of Dalwa that killed seven people, including children.
Another 190 suspects were allegedly involved in plots following bomb attacks on Shiite mosques in Qatif and Dammam, as well as an attack on Saudi security forces.
IS, which considers Shiites to be heretics, claimed responsibility for the mosque attacks.
On successive Fridays in May, two suicide bombings at mosques of the minority Shiite community in Eastern Province killed 25 people.
The jihadist group controls swathes of neighbouring Iraq and Syria, and has claimed widespread abuses including the beheading of foreign hostages.
It has expanded its operations in the region, also claiming an unprecedented attack on a Shiite mosque in Kuwait and several attacks in Yemen.
Saudi Arabia and its Sunni Gulf neighbours last year joined a US-led military coalition bombing IS in Syria, raising concerns about possible retaliation in the kingdom.
Interior Minister Crown Prince Mohammed bin Nayef said at the height of the attacks in May that Saudi Arabia's security remained "under control".
"Incidents such as this will not destabilise us. We have been through bigger ones," the minister said.
He led a crackdown on Al-Qaeda which waged a campaign of shootings and bombings against foreigners and Saudi security personnel between 2003 and 2007.