Osama Bin Ladenís father was a major building contractor in Saudi Arabia. Fifteen of the 19 hijackers on 11 September were Saudis. But given the secretive nature of the Saudi royal family, actions it has taken, including arrests, have not been widely publicised.
There were some tensions with the United States about the level of co-operation the Saudi police were giving. The Saudis blamed expatriate criminality for some unexplained incidents, including the death in a bomb attack of a British banker, but the suspicion remained that al-Qaeda elements or sympathisers were responsible.
The BBC's Security correspondent Frank Gardner explains the tensions within Saudia Arabia and its uneasy relationship with the US.
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