A suicide car bomb attack has killed at least four people and wounded up to 148 others in the centre of the Saudi capital, Riyadh.
Medical sources in the city said a senior Saudi security officer was among the dead.
A witness said he saw a car drive up to a barrier outside the headquarters of the Saudi security services, just before it exploded. The facade of the building was extensively damaged.
The Saudi authorities have denounced the attack as the work of terrorists.
Police have repeatedly clashed with Islamic militants around Riyadh in the last fortnight and officials said they have intercepted five vehicles packed with explosives.
Last week, the United States ordered non-essential diplomats and US citizens to leave the kingdom.
