By Paul Wood
BBC Middle East correspondent in Cairo
A message claiming to be from al-Qaeda says it is not to blame for a suicide car bomb attack in Riyadh last week.
Saudi security forces have been on high alert for al-Qaeda attacks
The tape does however warn of "fierce" attacks in 2004 against American and other western targets.
The tape, which can be heard on an Islamist website, says the attack on a police centre was a consequence of the Saudi rulers' "infidel policies.
Last week was the first time that the Saudi state has been directly targeted as opposed to a foreign target.
The tape says the Saudi royal family and its alliances with Christians and Jews was the reason for the attack.
Americans, Jews and "Crusaders", as western troops are called, will continue to be targeted by al-Qaeda, the tape says.
"This year, God willing, will be fiercer and harsher for them," it concludes.
Army of opponents
This tape, if authentic, does not contradict the original claim of responsibility for the Riyadh bombing, which came from a group called the al-Haramain Brigades.
They said they were just filling in for al-Qaeda, while it was preoccupied with its Jihad against crusaders.
Most analysts do not believe that a religious revolution is threatened in Saudi Arabia, but clerics in the country associated with the militants have claimed there are tens of thousands of armed men who want to get rid of the royal family.
These militants do not all belong to al-Qaeda but certainly sympathise with its world view.