Car Explodes in Riyadh

An unmarked police car exploded in the Saudi capital Monday, but there were no casualties, police said.

Nobody was in the car when it exploded in Riyadh's (search) eastern Al-Salaam district, and it was not known what caused the blast.

One officer told The Associated Press he heard a report on his police radio that a car sped by the parked vehicle and tossed an explosive toward it.

A Western diplomat told AP that a Saudi police officer appeared to be the target of the blast. Both the diplomat and the officer spoke on condition of anonymity.

Police were investigating the explosion, said Gen. Saad Abdullah al-Towaijiri, the chief of civil defense in the city, according to the official Saudi Press Agency (search) reported.

Earlier, some witnesses, speaking on condition of anonymity, said it appeared that two cars collided. They said they heard a crash and an explosion almost simultaneously. But police said only one car was involved.

The blast destroyed the car and shattered windows in nearby buildings, the Dubai-based Al-Arabiya satellite channel reported.

Security forces cordoned off the scene, and armored vehicles drove through the neighborhood. Police searched cars parked nearby and asked pedestrians in the area to present identification.

Islamic extremists have detonated four car bombs in Riyadh this year, killing 52 people, including the assailants, and wounding more than 100 others. The attacks on May 12 and Nov. 8 targeted housing compounds for foreigners.

Earlier this month, the U.S. State Department (search) recommended that nonessential American diplomats and the families of all U.S. officials in Saudi Arabia depart. It also recommended that private U.S. citizens consider leaving the country.