#Trending: Muslim world condemns suicide attack at Prophet's mosque
At least four people died in suicide bombing on a day that included two other attacks in Jeddah and Qatif.
The Prophet's Mosque, in the western city of Madina, is one of Islam's holiest sites - where Muhammad is buried and which attracts millions of visitors each year.
The governments of Egypt, Qatar, the United Arab Emirates, Bahrain, Kuwait, and Iran have all put out statements condemning the attack.
The Arabic-language hashtag #ISViolatesMosqueAndTombofProphet gained traction on Twitter shortly after the attack took place.
Translation: "They convinced [the bomber] that he had virgins awaiting him in heaven so he blew himself up in the radiant city just a few steps away from the Prophet's mosque, targeting men protecting the mosque and serving pilgrims."
Translation: "[IS'] flag bears the Prophet's name, may peace be upon him, and they then carry out an attack next to his grave. This is evidence that they have no religion or set of beliefs."
Translation: "God will curse all those violating the name of Islam and Muslims and shedding the blood of innocent people."
Since late 2014, Saudi Arabia has been hit by bombings and shootings claimed by the IS, however multiple attacks on the same day are unusual.
The Prophet's Mosque is particularly crowded during the Muslim holy month of Ramadan, which is supposed to be a time of charity and worship.
Undeterred by the blast at the sprawling Medina mosque complex, thousands of worshippers performed prayers on Monday night.