Three suicide attacks hit Saudi Arabia on July 4, including one near Islam’s second holiest site.
Four guards were killed near the Prophet’s Mosque in Medina, while only the bombers died in Jeddah and Qatif.
No group has yet said it was behind the attacks, but suspicion has fallen on ISIS.
The Sunni Muslim jihadist group has called for the overthrow of the Saudi monarchy and its supporters have previously carried out bombings in the Gulf state, targeting the Shia minority community and security forces.
ISIS has also claimed a series of deadly attacks in the predominantly Muslim countries of Turkey, Bangladesh and Iraq during the holy month of Ramadan.
In July 4 first bombing, two security officers were wounded when a man detonated an explosive vest he was wearing near the US consulate in the coastal city of Jeddah shortly after midnight.
An interior ministry spokesman identified the assailant as a 35-year-old Pakistani expat called Abdullah Qalzar Khan, who it said had worked as a private driver in Jeddah for 12 years.
The second attack took place near dusk outside a Shia mosque in the mainly Shia eastern city of Qatif.
A resident told the Reuters news agency that there were believed to be no casualties apart from the bomber, as worshippers had already left to break their daylight Ramadan fasts.
Not long afterwards, another bomber struck near the Prophet’s Mosque in Medina, where thousands of worshippers had gathered for the Maghrib prayers.
On July 5, the Senior Council of Ulema issued a statement saying those behind the three attacks, whom it described as “renegades”, “have no respect for any sanctity and they have no religion or conscience”.
The head of the Shura Council, Saudi Arabia’s main advisory body, said the attack was “unprecedented”.
The Grand Sheikh of Cairo’s al-Azhar University, the leading religious institute in the Sunni Muslim world, also stressed “the sanctity of the houses of God, especially the Prophet’s Mosque”.
The foreign minister of Shia power Iran, Saudi Arabia’s main regional rival,tweeted: “There are no more red lines left for terrorists to cross. Sunnis, Shiites will both remain victims unless we stand united as one. #Medina.”
Saudi Arabia’s Crown Prince and Interior Minister, Mohammed bin Nayef bin Abdul Aziz, meanwhile sought to reassure his fellow citizens, saying: “The security of the homeland is good, it is at its highest levels and thanks be to God it gets stronger every day.”
According to the official Saudi Press Agency, the prince made the statement while visiting the security officers wounded in the Jeddah bombing.