Five security service agents have been killed and two others injured after a shootout in the Saudi capital Riyadh.
The Interior Ministry said one alleged militant and other suspects were detained in the raid, in which a sixth person was also killed.
It was carried out after authorities got a tip-off that a wanted militant was hiding in a villa.
The agents are thought to have come under fire while approaching the house with the man's father.
Two hand grenades, two machine-guns and five pistols were found at the house, the ministry said in a statement carried by the official Saudi Press Agency.
As the unit was completing its task, [it came] under heavy fire from unknown elements," the statement added.
An unnamed official told the Reuters news agency that the captured militant was "very important", although he said he was not on the list of 24 most wanted suspects released by the Saudi authorities.
Twenty-six suspects were originally named, but two have already been killed in a shootout with the authorities.
Saudi Arabia has been dealing with an upsurge in violence by Islamic militants who US officials say are linked to Saudi-born Osama bin Laden's al Qaeda network.
More than 50 people - including the bombers and many foreigners - were killed in two attacks against residential compounds in Riyadh in May and November last year.