As many as four explosions rocked Riyadh hours before U.S. Secretary of State Colin Powell was scheduled to arrive in Saudi Arabia.
Saudi security officials say at least three compounds housing Westerners were targeted.
Officials say several people were wounded in the incidents that started late Monday, but there are no immediate reports of deaths. The Saudi Arabian Interior Ministry is investigating.
The U.S. State Department says it believes the explosions at the compounds were caused by car bombs.
U.S. State Department officials say there have been no reports of Americans wounded in the blasts.
Earlier this month, the State Department warned Americans against traveling to Saudi Arabia because of increased terrorism concerns. Also this month, Saudi police seized a large weapons cache as they searched for 19 men believed to be involved in terror plots in the kingdom.