Saudi Arabia has detained 88 people, more than half of them Saudis, on suspicion of plotting "terrorist" attacks at home and abroad, the interior ministry said on Tuesday.
Ministry spokesman Major General Mansour Turki told a news conference that 48 of those arrested were Saudis, and that many had been planning assassinations.
A ministry statement carried by the official Saudi Press Agency said the ministry had been following a number of suspects in view of what it called the spread of "strife and sick ideas" that lured members of the community "to places of strife".
Riyadh has long expressed fears of being targeted by Islamist jihadists, including by some of its own citizens, who have taken part in insurgencies in Iraq and Syria.
Saudi King Abdullah warned on Saturday that terrorism would soon spread to Europe and the United States unless it was quickly dealt with in the Middle East.