A leading U.S. defense contractor has confirmed nine of its employees, including seven Americans, were among those killed in Monday night's terrorist bomb attacks in Saudi Arabia.

Nine employees of the Vinnell Corporation, seven Americans and two Philippines citizens, were killed in the terror attack. In addition, several more were injured, of whom 15 remain hospitalized, two in serious condition.

The Northrop Grumman Corporation, which owns Vinnell, says in a statement a residential and office facility used by the firm in Riyadh was one of three compounds attacked. Although it says a number of family members of Vinnell workers live in the compound, none were harmed.

A Northrop executive says the firm is deeply shocked by what he calls "this senseless attack."

Vinnell is under contract to the U.S. Army to provide training services to the Saudi National Guard. The company employs about 800 people in Riyadh, of whom 300 are U.S. citizens.

Vinnell has been involved in military training in Saudi Arabia since 1975. Its latest contract was a multi-year deal worth some $830 million.

Its American employees have been recruited from among former service members skilled in such areas as armored vehicle and missile operations and maintenance, military intelligence, health services and other specialties.

The U.S. military has had some 5,000 personnel in Saudi Arabia but recently announced plans for their withdrawal.

The Pentagon has had no comment on the attack on Vinnell's Riyadh compound, saying no American soldiers were targeted.