Two explosions tore through the Saudi Arabian National Guard building early this morning in Riyadh, killing six people, five of them American workers. U.S. Ambassador Ray Mabus confirmed that an explosive device had been found. The blast wounded at least 60 people, including 34 Americans. The attack targeted a building where retired and active U.S. military personnel advise and train the Saudi National Guard, an organization whose chief purposes are to protect the Saudi monarchy and maintain domestic order. Two groups have claimed responsibility. One, a previously unknown organization calling itself the Tigers of the Gulf, said it wants to drive Americans out of Saudi Arabia. There are other possible suspects, including Shia Muslims and Sunni fundamentalists unhappy with the rule of King Fahd. President Clinton said the U.S. would "devote an enormous effort" to finding out who is responsible: "We have expressed our condolences and deep regret to the families of those who were killed."