A Saudi security officer has been killed in a shoot-out with wanted militants, according to officials.
Five men were arrested, including two suspected al-Qaeda sympathisers, the Saudi Interior Ministry said.
"One security officer was martyred while eight of his comrades were injured," said a ministry spokesman.
The arrests are part of a crackdown on militants following a series of bloody attacks on residential compounds in Riyadh last year.
The gunbattle took place at a house in Unayzah, 230 miles north of the capital Riyadh, where security forces uncovered an arms cache.
Police seized automatic rifles, pistols, pipe bombs, ammunition, computers, communications equipment and 38,000 riyals (US$10,000) in the operation.
The men fled the house in a car but were chased by security forces to an unnamed desert location where they were detained. One of them was seriously injured.
More than 100 people have died in violence since May 2003, many of them foreign civilians.
Many senior militants have been killed or arrested in the campaign, including more than half of a list of 26 most-wanted terrorists.
It was not immediately clear whether those arrested Wednesday were part of that list.