At least four explosions rocked the capital of Saudi Arabia late Monday night and witnesses say there are several people wounded. Officials say the blasts occurred at compounds housing Westerners.

According to news reports at least one of the explosions was caused by a car packed with explosives that rammed into a residential compound housing mostly westerners and non-Saudis.

Witnesses were quoted as saying the blasts shook nearby buildings. Soon afterwards, ambulances were heard speeding to the scene.

The explosions occurred on the eve of Secretary of State Colin Powell's planned visit to Saudi Arabia. Mr. Powell is seeking greater cooperation in the fight against terrorism and support for the Israeli-Palestinian peace plan.

The secretary is in Amman, Jordan, and it was not immediately known if he would go ahead with the visit to Saudi Arabia Tuesday as planned.

Earlier this month, the State Department warned Americans against traveling to Saudi Arabia because of increased concerns regarding terrorism.

Last week, Saudi security forces seized large quantities of explosives and weapons in the capital while searching for as many as 19 suspected terrorists, including 17 Saudis.