|Saudi Arabia's intelligence agencies are so infiltrated by al-Qa'ida sympathisers that the kingdom's counter-terrorist campaign is failing and militant operations are spreading into neighbouring states, senior Arab and Western officials have warned.
The main Saudi intelligence organisation responsible for combating al-Qa'ida at the Interior Ministry is riddled with agents linked to the militants, the officials say.
"Their staff is 80 per cent sympathetic to al-Qa'ida," one senior Arab source said.
"All Saudi intelligence agencies are compromised. To fight al-Qa'ida they will need to start from scratch. I'm not hopeful the Saudis will win this one."
The level of penetration in the security forces is highlighted by the number of former police and military men on the Interior Ministry's list of the 26 most-wanted terrorists. They include Othman al-Amri, a former sergeant, who was No21 on the list and handed himself in last week as part of a royal amnesty, and Saleh al-Oufi, the leader of an al-Qa'ida cell, who is a former police officer.
Saudi Arabia has been shaken by a series of terrorist attacks over the past year that have targeted foreign workers. Now there is evidence the campaign of suicide bombings, kidnappings and shootings is spreading from the kingdom to neighbouring countries, where many expatriates have moved for safety.
The Pentagon is preparing to evacuate 650 non-essential personnel and families from Bahrain, where the US Fifth Fleet is based.
The US embassy in Manama has urged all US citizens to consider leaving Bahrain because of "information" that extremists are planning attacks against US and other Western interests.
"I'm most concerned about Bahrain. If I was a Bahraini, I would worry," said a senior Arab official from one of Saudi Arabia's neighbours.
"After that, Kuwait and the United Arab Emirates are also vulnerable."
Evidence has emerged that Saudi Arabia is al-Qa'ida's main regional hub for recruiting, training, funding and arming its militant cells.
Several Saudi volunteers who slipped across the border into Iraq have been killed fighting US forces in the Iraqi city of Fallujah.
Militants on both sides of the border have adopted identical tactics, such as suicide bombings, beheading Western hostages and dragging victims behind cars.
"We're sure these are not copycat tactics being used here. This is a co-ordinated operation," said a senior Saudi official. "These groups do not just exchange information - they also reinforce each other with trained personnel."
Jordan, too, is in the firing line. The Jordanians have intercepted several al-Qa'ida teams that have infiltrated the country from Saudi Arabia with the aim of whipping up opposition to Jordan's leadership among the southern clans, which have tribal links across the border.
Although the FBI, the CIA, British intelligence, Scotland Yard's anti-terrorist squad and other foreign agencies are collaborating with the Saudis, they still face obstruction from local security services in investigating terrorist attacks.