Security forces in the Saudi Arabian capital Riyadh have killed five suspected militants believed to be linked to an attack on an oil plant.
Security forces were engaged in a two-hour shoot-out, witnesses said
Security sources say a siege took place at a villa in a Riyadh suburb in which shots were fired and grenades thrown.
The Saudi interior ministry said one other suspect had been arrested elsewhere in the capital.
An Islamic website has claimed al-Qaeda was behind the foiled attack on Friday on an oil processing plant in Abqaiq.
Interior ministry spokesman Maj Gen Mansour al-Turki said two simultaneous raids had taken place on Monday morning, leading to the deaths of five suspects in a shoot-out and the arrest of a sixth.
"We think all the men involved had something to do with the Abqaiq attempt," he said.
"The shoot-out is over now. We will interrogate the arrested man."
An interior ministry statement described how security forces "stormed a building in east Riyadh which a criminal gang was using as a centre for attacks and corruption".
"All five were killed after an intense exchange of fire," it said
Witnesses said they heard the sound of heavy gunfire and what seemed to be mortars as security forces surrounded the villa in an eastern suburb of Riyadh, in a fire fight lasting about two hours.
"Around the time of dawn prayers, we heard the sound of shots and saw the sky light up. Then a short time later there were heavy explosions," journalist Odwan al-Ahmar told Reuters news agency.
A large quantity of arms and ammunition was said to have been seized from the villa.
The Riyadh operation followed Friday's attempt by militants to carry out a suicide bomb attack at the largest oil-processing plant in eastern Saudi Arabia.
The attack at Abqaiq was foiled when guards opened fire on cars carrying explosives as they tried to ram the gates.
At least one of the vehicles blew up, killing the occupants. Two guards were also killed, and another two wounded.
The Saudi government said output at the plant had not been affected.
An interior ministry statement said the two bombers killed were on a list of the 15 most wanted al-Qaeda-linked terrorists issued by the Saudi authorities last June.
A website frequently used by Islamic militants said the al-Qaeda network was responsible for the attack on Abqaiq, although the claim could not be verified.
In a statement, the website said the operation was part of al-Qaeda's campaign to force "infidels" out of the peninsula.
The al-Qaeda network on the Arabian Peninsula has long called for attacks on Saudi oil installations.