Saudi Arabia says it has foiled a plot by militants to carry out suicide air attacks on oil installations and military bases.
Foreign nationals were among 172 terror suspects held in a series of raids, the interior ministry said on state TV.
Large amounts of weapons and $32.4m (Â£16.21m) in cash were also seized.
The Saudi authorities have been battling al-Qaeda since a wave of bombings and shootings rocked the kingdom in 2003.
The attacks in 2003 and since have claimed the lives of nearly 300 security personnel, militants and Saudi and foreign civilians.
BBC Middle East analyst Roger Hardy says the Saudis periodically claim to have crushed the insurgency but although they have shut down part of the network the persistence of the attacks suggests the problem is deep-rooted.
The Saudi authorities said the fresh plots it had foiled were at an advanced stage.
“Some [militants] have begun training on the use of weapons, and some were sent to other countries to study aviation in preparation to use them to carry out terrorist operations inside the kingdom,” a ministry statement read out on state TV channel al-Ekhbaria said.
Some of the military targets were outside the kingdom, it added, without specifying where.
The station broadcast footage of various types of weapons, including plastic explosives, ammunition cartridges, handguns and rifles wrapped in plastic sheeting, which were said to have been buried in the desert.
Interior ministry spokesman Gen Mansur al-Turki said the suspects were “linked to foreign elements… not necessarily directly to al-Qaeda, but you know, there are many al-Qaeda and terrorism activities going on”.
“The deviant group… takes advantage of trouble spots outside the kingdom in planning, recruitment and training,” Gen Turki said, apparently referring to Iraq.
He added: “Some individuals were training to fly to carry out terrorist attacks… Some of the cells arrested planned to target oil installations and refineries.”
Gen Turki said there were also plans to attack a prison and release the inmates.
Al-Qaeda leader Osama Bin Laden, a Saudi himself, has called for attacks against the oil-rich kingdom because of its close ties to the West.
Our correspondent, Roger Hardy, says many ordinary Saudis are appalled by the group’s violent methods but some of the disaffected young or from part of the powerful Wahhabi religious establishment have offered support.
Most of the 19 al-Qaeda militants who carried out the suicide plane attacks in the US in September 2001 were Saudis.