Saudi Arabian security forces battled suspected Islamic extremists across the country on Thursday.
The encounters saw two wanted militants killed in Riyadh. Forces also clashed with armed men in the holy city of Medina.
The kingdom's interior ministry officials said at least one suspected militant was arrested in Riyadh and an unspecified number were detained in Medina, west of the capital, where the country's new monarch, King Abdullah, is visiting.
Ministry spokesman Mansour al-Turki said a firefight began in Riyadh after security forces launched an early morning raid on a villa at Al-Massef, a northern residential area of the capital.
"The police suspect that one or more of the wanted elements are in this place," al-Turki told The Associated Press. It was unclear if he was talking about the government's list of 36 most wanted militants, sought in connection to terror attacks against the kingdom in 2003.
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Another security official, speaking on condition of anonymity, said two militants were killed in the shootout, during which a hand grenade was thrown at the police but did not explode.
The nationalities of the slain militants and a third who was arrested while trying to flee the scene were not immediately clear. Police helicopters hovered overhead as security forces sealed off the area preventing pedestrians or vehicles from entering or leaving the scene, as more militants are believed to be inside.