FBI agents are helping in the search for the people behind the suicide bomb attacks on compounds housing Westerners in Saudi Arabia.
The prime suspect for the bombings is Osama Bin Laden's al-Qaeda network. The BBC's security correspondent, Frank Gardner, assesses the prospects of catching the culprits and the relationship between Saudi Arabia and al-Qaeda.
How much co-operation can the FBI team expect from the Saudis?
A lot more than they would have done in the past. The history of FBI and Saudi co-operation is not a happy one.
In the mid-1990s there were two major bombings in Saudi Arabia.
A bomb went off in a Saudi National Guard training centre killing some Americans and Indians in November, 1995. The Saudis rounded up some suspects and executed them before the Americans could talk to them.
Then, in June, 1996, there was the al-Khobar Towers bombing, killing 19 servicemen and injuring several others.
The FBI has always complained they never got full co-operation because of the Saudis' obsession with secrecy, and partly also with national pride.
They made their arrests but did not share their information with the Americans.
This time, though, post-11 September - and due to the fact that 15 of the 19 suicide hijackers came from Saudi Arabia - I think pressure from Washington will be enormous. And I think the Saudis will co-operate.
Is it true that some in the Saudi Government are sympathetic to al-Qaeda, even paying them off not to operate in Saudi Arabia?
There are two aspects to this.
There are very close links between Saudi Arabia as a country and al-Qaeda. Remember that al-Qaeda grew out of an organisation that the West encouraged.
The West encouraged people like Osama Bin Laden in the 1980s to fight the Soviets in Afghanistan.
Money was channelled quite openly from across the Gulf to help the Mujahideen confront the Soviets.
After 1990 this force, headed by Bin Laden, was effectively out of a job. The Soviets had left; they were looking for a new cause.
When Iraq invaded Kuwait, they said, 'we'll do the job', the Saudis said 'no thanks, we're getting the Americans in', and Bin Laden started to turn against the Saudi ruling family.
But throughout the 1990s, charitable funding continued by many philanthropic donors who did not check too carefully where the money was going.
Money was being sent to madrassas [Koranic] schools, in Pakistan and Afghanistan.
A lot ended up in al-Qaeda hands.
In terms of sympathy for al-Qaeda, it runs pretty strong in Saudi Arabia. Not at the top levels of government who have everything to fear from al-Qaeda - which would like to replace the al-Saud dynasty with a more purist Islamic government, as well as seeing Westerners leave.
But there is a big groundswell of sympathy for al-Qaeda among the middle and lower levels of the security system, specifically the Interior Ministry in Saudi Arabia.
What about the competence of the Saudi authorities, bearing in mind they allowed a large number of suspects to escape from a recent raid?
I'm afraid it shows that either they made a massive bungle in that operation on 6 May, or that somebody inside the Saudi security service tipped off the gunmen.
There was a big shoot-out in Riyadh with 19 known members of an organisation calling themselves the Mujahideen of Arabia.
The Saudi authorities published photographs of the people they wanted.
They managed to seize a stash of 800lbs (400 kilos) of explosives, plus a whole range of weapons, but they never actually caught any of these people.
One of them has since surrendered and is being interrogated.
These people have been at large for a week, and almost certainly have a connection with those who attacked the compounds on Monday night.
How these people got away after such a gun battle, in a country that is obsessed with internal security, is very suspicious indeed.
What about the claims in Britain that the arrests of several Britons on bombing charges - which according to the Saudis is related to illegal drinking - shows the Saudis do not really recognise the problem of internal terrorism?
The five or six Britons who have been incarcerated on terrorism charges inside Saudi Arabia for the last two years represent a travesty of justice - which the Foreign Office has been almost totally ineffective at reaching a solution to.
They have not ignored the problem and have tried very hard, behind closed doors to resolve this, but so far only one Briton has been released - Gary O'Nions, who was never accused of terrorism anyhow.
These people, with one possible exception, have been made scapegoats for a wave of domestic unrest aimed at embarrassing the Saudi ruling family.
There is no doubt in my mind - and in the minds of the British Government - that the Britons imprisoned in Saudi have nothing to do with the bombings they were accused of.
Yes, they are guilty of alcohol charges, they admit that. They broke the law in Saudi, they were caught red-handed and they know they deserve to be punished - but it was nothing to do with terrorism.
George Bush recently said the tide was turning against al-Qaeda. Do these explosions indicate the tide is still coming in?
It is hard to say which direction it is going in.
There have been a lot of successes for the West over the war on terrorism.
After all, they have driven al-Qaeda out of Afghanistan - or at least out of their training camps there.
So the biggest recruiting tool that al-Qaeda had, which was to encourage thousands of impressionable young men to learn to fire a Kalashnikov in the wilds of Afghanistan, has gone.
They have caught a lot of the operational chiefs - Khalid Sheikh Mohammed, Ramzi Binalshibh, Abu Zubaydah - who are being interrogated, and which has lead to more arrests and to the foiling of more plots.
The problem is that al-Qaeda is like a state of mind.
If you are a Muslim and you are angry at the perceived injustices inflicted upon your people - the Palestinians, Iraq, Chechnya, Kashmir and Bosnia - and you blame the West for it, then al-Qaeda offers you a means to do something about it violently, to take some kind of revenge.
We are only talking about a tiny minority of Muslims, and most Muslims condemn al-Qaeda, but nevertheless it is there as a possible route.
I think what we are seeing in Saudi Arabia is quite possibly a self-contained cell, who may be acting with the approval of al-Qaeda's rump leadership left in Pakistan.
They have taken matters into their own hands and executed a very well organised plan to try to drive Westerners out of Saudi Arabia, and embarrass the Saudi Government to eventually bring about its downfall.