Qaeda- linked groups in Yemen, achieved over years of fighting domestic insurgency, appears to have enabled Riyadh to provide warning of a parcel bomb plot against the United States, analysts said. Two parcels containing explosives, addressed to synagogues in Chicago and sent from Yemen, were intercepted in Dubai and Britain on Friday after an intelligence tipoff. Washington said Saudi Arabia, a key US ally and the world's top oil exporter, had helped to determine that the threat came from impoverished Yemen, home to a resurgent Al-Qaeda wing that claimed responsibility for a failed plot to blow up a US plane headed for Detroit in December. Riyadh-based Western diplomats said collaboration between the Gulf Arab kingdom and Western intelligence services has been strong since foreign experts helped Saudi Arabia crush an Al-Qaeda campaign targeting oil facilities, embassies and expatriate housing compounds that lasted from 2003 to 2006. “The cooperation is a continous matter. What is new is that Saudi intelligence has surely penetrated Al-Qaeda in Yemen,” said prominent Saudi journalist Jamal Khashoggi. Only two weeks ago, France said it had received warnings from Saudi Arabia that Al-Qaeda was targeting Europe. US President Barack Obama called Saudi King Abdullah on Saturday to discuss the parcel bomb plot. Along with the United States, which over the past year has raised military and logistical aid to Yemen, Saudi Arabia is the other foreign power that wants to see Yemen eradicate Al-Qaeda. The group's Yemen branch last year tried to assassinate Saudi counter-terrorism chief Prince Mohammed Bin Naif, the first known attack on a member of the royal family since Al-Qaeda started its campaign in 2003. A Saudi suicide bomber who had returned to Saudi Arabia from Yemen posing as a repentant militant blew himself up in the prince's Jeddah office. Although the royal escaped unharmed, analysts and diplomats say the attack was a major shock to the authorities and their intelligence apparatus. “The attack was a wake-up call for the Saudis. They have become very professional. They have inflitrated tribes that protect Al-Qaeda,” said Dubai-based security analyst Theodore Karasik.