A suicide bombing outside one of Islam's holiest sites killed four Saudi security forces, and similar attacks outside a Shi'ite mosque and a U.S. Consulate in two other Saudi cities raised fears of a coordinated assault on the kingdom.
The Interior Ministry said five others were wounded in the attack outside the sprawling mosque grounds where the Prophet Muhammad is buried in Medina on July 4. Millions of Muslims from around the world visit the mosque every year as part of their pilgrimage to Mecca.
The ministry said the attacker set off the bomb in a parking lot after security officers raised suspicions about him. Several cars caught fire and thick plumes of black smoke were seen rising from the site of the explosion as thousands of worshippers crowded the streets around the mosque.
No group has yet claimed responsibility for any of the attacks.
The series of explosions came as Muslims celebrated the holiest day during the holy month of Ramadan and followed mass killings claimed by the Islamic State group in Turkey, Bangladesh, and Iraq in the past week.
The attacks all seem to have been timed to coincide with the approach of Eid al-Fitr, the holiday that celebrates the end of the Islamic holy month.
Saudi television showed that thousands of worshipers in Medina were undeterred by the blast at the mosque and performed prayers only a few hours after it occurred.
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.
A Saudi 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.
A video circulating on social media and purporting to show the aftermath of a Qatif blast showed an agitated crowd on a street, with a fire raging near a building and a bloody body part lying on the ground.
Hours earlier a suicide bomber was killed and two people were wounded in a blast near the U.S. Consulate in the kingdom's second city, Jeddah.
A Saudi security official said the attacker parked a car near the consulate and a mosque in Jeddah before detonating the device.
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.
A U.S. official said no American citizens or consulate staff were hurt in the Jeddah blast.
General Mansour al-Turki, the Saudi interior ministry spokesman, told state Al-Ekhbaria news channel that the suspect was closer to a mosque in the area than to the American consulate.
He also said that "devices that failed to explode [were] found in the vicinity of the site."
While no group has claimed responsibility for any of the attacks, the Interior Ministry implied that it suspected the Islamic State militant group by condemning "straying elements," its usual term for Is and its rival Al-Qaeda network.
IS 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.
Police and groups of local volunteers increased security near mosques in Qatif after suicide bombings hit mosques in Shi'ite areas last year, killing dozens. Another suicide blast at a mosque used by security forces killed 15 a year ago.