Witnesses in the Saudi capital, Riyadh, say several people have been killed in a car bomb explosion that went off outside the Saudi security headquarters.
Reports from the scene say the blast left the security building engulfed in flames and shattered windows in nearby buildings.
Ambulances are at the scene treating dozens of wounded people.
Saudi authorities have fought a running battle with militants and Islamic extremists over the past year. Saudi police say they have seized and defused five car bombs within the past week.
Last week, the U.S. State Department ordered all non-essential diplomats to leave Saudi Arabia because of security concerns.
Suicide bombings at foreign residential compounds in Riyadh last year killed more than 50 people.