A damaged car is seen after a blast near the US consulate in Saudi Arabia's second city of Jeddah July 4, 2016. [Photo/Agencies]

Other pictures circulating on social media showed dark smoke billowing from flames near the Mosque of the Prophet, originally built in the 7th century by the Prophet Muhammad, who is buried there along with his first two successors.

In Qatif, an eastern city that is home to many members of the Shi'ite minority, at least one and possibly two explosions struck near a Shi'ite mosque. The security spokesman said the body of a bomber and two other people have been identified, without providing any more details.

Witnesses described body parts, apparently of a suicide bomber, in the aftermath.

Authorities identified the attacker as a 34-year-old Pakistani driver named Abdullah Qalzar Khan, who lived with his wife and family in the city.

An official of the US State Department said no American citizens or consulate staff were hurt in the Jeddah blast. He said the United States was aware of reports of explosions in Qatif and Medina and would monitor the situation closely.

He said the State Department encouraged US citizens in Saudi Arabia "to be aware of their surroundings, and keep security and situational awareness levels high."

Islamic State has carried out a series of bombing and shooting attacks in Saudi Arabia since mid-2014 that have killed scores of people, mostly members of the Shi'ite Muslim minority and security services.