A bomb was found attached to the bottom of a car belonging to an American hospital worker, and what was termed a "suspicious object' was located stuck to the underside of a Briton's vehicle, according to a U.S. Embassy security circular obtained by The Associated Press on Sunday. The devices were removed without incident, the circular said, adding that both incidents occurred over the weekend.

The discoveries followed close upon the June 20 car bombing that killed a 35-year-old British banker in a Riyadh, the Saudi capital.

The circular said an American employee at the King Faisal Specialist Hospital in Riyadh found an explosive device attached to his car Saturday.

Saudi police were contacted about both finds, removed the devices and were investigating. The names of the Americans and Briton were not immediately known.

Saudi officials were not immediately available for comment.

Increased terror concerns linked to Saudi Arabia have surfaced in recent weeks after the arrest of three Saudis in Morocco in a widening investigation of an alleged al-Qaida plot to attack U.S. and British warships in the Strait of Gibraltar.

Saudi authorities have also detained 13 people - 11 Saudis, a Sudanese man and an Iraqi - for allegedly planning to attack vital installations in the oil-rich state by using explosives and surface-to-air missiles.

In May, Saudi security guards found a missile launcher tube about two miles from a runway at Prince Sultan Air Base, the U.S. military's regional command-and-control center and home to about 4,500 U.S. troops and several military aircraft.

The detained Sudanese man has reportedly confessed that he and six of the arrested Saudis were linked to al-Qaida, the terror network headed Osama bin Laden- the dissident Saudi and prime suspect in the Sept. 11 attacks on the New York and the Pentagon. .

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The discovery of suspicious devices attached to two cars belonging to an American hospital worker and a British expatriate followed close upon the June 20 car bombing that killed a 35-year-old British banker in a Riyadh, the Saudi capital.