RIYADH, June 8: Gunmen killed an American working for a US company in the Saudi capital Riyadh on Tuesday, the fifth attack on Westerners and other foreigners in the world's top oil exporter in five weeks.

The latest killing in the kingdom, which has been battling to stamp out attacks by Saudi-born Osama bin Laden's Al Qaeda for more than a year, was likely to heighten fears among tens of thousands of expatriates, many of whom work in the oil industry.

The American worked for US contracting firm Vinnell, a unit of Northrop Grumman Corporation that trains the Saudi National Guard, an elite force protecting the pro-US monarchy.

Police said the American was killed when shots were fired at him outside his house in eastern Riyadh. Witnesses said the gunmen followed the American in a car when he left a clinic to go to his villa in the Rawda area and shot him when he got out of his vehicle.

Dubai-based Al Arabiya television said the gunmen fired nine shots, two of which hit the American's head. "We can confirm that an employee of Vinnell Arabia was shot and killed by an unknown assailant," Vinnell spokesman Jay McCaffrey said from the company's offices outside Washington.

On Sunday, suspected Al Qaeda gunmen killed an Irish cameraman Simon Cumbers, 36, and critically wounded BBC security correspondent Frank Gardner, 42, in a Riyadh area known as a militant stronghold. -Reuters