Three suicide bombers struck in Saudi Arabia on Monday, including a shocking attack at Islam's second holiest site, the Prophet's Mosque in Medina, where four security guards were killed.
The attacks on Islam's spiritual home came as Muslims prepare for the feast this week marking the end of the holy fasting month Ramadan.
Other two blasts occurred in the Red Sea city of Jeddah near the US consulate and in Shiite-dominated Qatif on the other side of the country.
There were no claims of responsibility, but the Islamic State group had urged its supporters to carry out attacks during the holy month and has claimed or been blamed for a wave of Ramadan shootings and bombings including in Orlando, Bangladesh, Istanbul and Baghdad.
The suicide bombing in Medina came during sunset prayers at the Prophet's Mosque -- where Islam's Prophet Mohammed is buried and which attracts millions of pilgrims each year.
The Saudi interior ministry said in a statement that security forces became suspicious of a man who was heading for the Prophet's Mosque through a parking lot.
"As they tried to stop him, he blew himself up with an explosive belt causing his death and the death of four security personnel," the statement said, adding that five others were injured.
The ministry said the attack was carried out by a Pakistani resident identified as Abdullah Qalzar Khan, a 35-year-old private driver who had been living with his wife and her parents in Jeddah for 12 years. The statement didn’t elaborate.
Interior ministry spokesman General Mansour al-Turki told state news channel Al-Ekhbaria that the bomber was closer to a mosque in the area than to the consulate.
The ministry said in the statement published on the official SPA news agency that the bomber's explosive belt had "partially" exploded.
The head of Saudi Arabia's Shura Council, the kingdom's main advisory body, said the attack was "unprecedented".
"This crime, which causes goosebumps, could not have been perpetrated by someone who had an atom of belief in his heart," Abdullah al-Sheikh said.
Iran, the main Shiite power, also condemned the bombings and called for Muslim unity against extremists.
"There are no more red lines left for terrorists to cross. Sunnis, Shiites will both remain victims unless we stand united as one," Iranian Foreign Minister Mohammad Javad Zarif said on Twitter.
At about the same time as the Medina blast, another bomber killed himself in Qatif, residents there said.
"Suicide bomber for sure. I can see the body torn apart," said one witness to the attack in Qatif.
Another resident told the media that "one bomber blew himself up near the mosque", frequented by Shiites in downtown Qatif on the Gulf coast.
No bystanders were hurt, she said.
Monday's first bombing, near the US consulate in Jeddah, was carried out not by a Saudi but by a "resident foreigner," General Mansour al-Turki, the interior ministry spokesman, told Al-Arabiya.
The US embassy in Riyadh reported no casualties among consulate staff. The attack coincided with the US July 4 Independence Day holiday.
Since late 2014 a series of bombings and shootings claimed by IS in Saudi Arabia has targeted minority Shiites as well as members of the security forces, killing dozens of people.
Most of the attacks have been staged in Eastern Province, home to the majority of Shiites in the Sunni-majority Gulf state.