Explosions severely damaged the headquarters of Saudi security Wednesday, killing at least 10 people and injuring dozens, a police official confirmed. Initial reports indicated the blasts came from at least one car bomb, which exploded at a protective barrier outside the HQ. Witnesses said the explosions, which occurred about 2 p.m. local time, shattered windows and damaged walls in surrounding buildings. Clouds of black smoke rose from the site and settled over the neighborhood, and security forces evacuated surrounding buildings. Firefighters worked to extinguish the blaze that engulfed the General Security building. Over 20 ambulances rushed to the scene and two helicopters patrolled above. Washington last week ordered the departure of nonessential U.S. government employees and family members from Saudi Arabia. It also urged private citizens to leave the kingdom, and the U.S. Embassy in Riyadh issued an advisory warning of "credible indications of terrorist threats aimed at American and Western interests in Saudi Arabia." **PHOTO CAPTION*** Saudi rescue vehicles and personnel are seen in front of the destroyed headquarter building of the general security services in Riyadh, following a car bomb explosion. (AFP)