With a series of bombings during the past week, the Islamic State has killed hundreds of Muslims.

And they have not been collateral damage – they have been the main targets.

From Istanbul to Saudi Arabia, Baghdad to Bangladesh, the Islamic State has been linked to or is suspected in attacks that deliver a clear message of intimidation to fellow Muslims. They are part of a growing campaign to silence leading Islamic voices who challenge the group’s narrow, apocalyptic interpretation of Islam.

The car bombs, raids, and suicide attacks have come at the close of Ramadan, Islam’s holy month, and have included a strike on one of Islam’s holiest sites, the mosque holding the prophet Muhammad’s tomb in Medina, Saudi Arabia.

It is a stark reminder that, in the self-declared Islamic State’s efforts to establish a caliphate, it is rival Muslims – who fail to join their jihad – who are a much greater enemy than non-Muslim "infidels."

So far, this threat has been largely glossed over by regional governments embroiled in suppressing dissent at home or taking sides in proxy wars in Yemen and Syria. The question now is whether the brazenness of the recent attacks will prompt a more aggressive response from regional powers.

The end-of-Ramadan spate of violence began last week when terrorists traveling from the IS "capital" of Raqqa killed 45 at Istanbul’s Ataturk Airport. Overnight Friday, terrorists claiming affiliation with IS killed 20 patrons and two police officers at a bakery in Dhaka, Bangladesh.

This weekend, IS claimed responsibility for a truck bomb in Baghdad that killed 215, the city’s deadliest in a decade. And three suicide bomb attacks in Saudi Arabia in 24 hours – including the one in Medina – have not yet been connected to IS, though the group is seen as the leading suspect.

Saudi in the crosshairs

At first glance, the targeting of the Prophet’s Mosque, which also houses the tombs of the first two caliphs, Abu Bakr and Omar bin Khattab, appears to run counter to the Islamic State’s ultra-orthodox ideology. According to a saying ascribed to the prophet, “Medina is a sanctuary. Whoever commits sin in it will incur the curse of God, the angels, and all the people.”

Yet IS has long reserved much of its vitriol for Saudi Arabia’s royal family and state-approved clerics, and it has been willing to go to great lengths to target them.

Saudi’s ultraconservative interpretation of Islam, Wahabism, mirrors some of the extremist interpretation by IS, some observers say. But IS itself argues that the clerics do not go far enough, and that their nonviolent ways are a “betrayal.”

“The palace scholars of the Saudi regime … are at the forefront of this effort to dissuade Muslims from jihad,” claimed the January issue of Dabiq, IS’s official propaganda magazine.

“In the severest terms, they have advised the youth to reject the true meaning of jihad and to replace it with national pride,” it added.

Saudi Arabia’s close relationship to the West is also a point of contention. But more deeply, the religious zealots of IS see the House of Saud as their biggest competitor.

The royal family acts as custodians of Mecca and Medina (the two holiest sites in Islam) and of a robust and respected religious establishment. Saudi Arabia is home to leading Islamic universities and voices.

So long as the House of Saud maintains its preeminent status in the Islamic world, IS will continue to struggle to present itself as the true voice of Islam, or a legitimate caliphate.

Moderate ‘hit list’

The attack in Dhaka, meanwhile, was carried out by terrorists who decried Bangladesh’s secular traditions. More broadly, IS has vowed to kill Muslims it sees as apostates.

In March, it issued a hit list of 11 leading imams and Muslim thinkers in the West it accused of apostasy due to their nonviolence and rejection of IS ideology.

IS’s intolerance for any strain of Islam but its own is further apparent in its characterization of the conservative Muslim Brotherhood as a disease that has spread since its founding in Egypt in 1928.

IS singles out the Brotherhood for leading “the deviant call to interfaith among Muslims, Christians, and Jews” and for participating in democracy, “a religion that gives supreme authority to people rather than Allah,” in the February issue of Dabiq.

“While the crusaders have been the most apparent adversary of the Muslims for the past thousand years, one must never forget the original enemy of Islam and its nation. Shaytan [Satan], through his cunning and experience with kufr [infidels], has always tried to infiltrate the Ummah [global community of Muslims].”

Shiite ‘obsession’

Sunday’s truck-bombing in Baghdad marked IS’s largest attack ever.

It was seen partly as retaliation for the loss of Fallujah, which fell to Iraq security forces and Shiite militias earlier this month. But it also comes from a deep-seated hatred of Shiites that is at the core of IS ideology, and which makes Shiite-majority Iraq a main target.

IS’s obsession with Shiites distinguishes it from other Islamist and jihadist groups and is the foundation of its self-purported image as “defenders of Sunnis.” The origins go back to the group’s founding as Al Qaeda in Iraq in 2004, as leader Abu Musab Zarqawi began targeting Iraq’s Shiites against the wishes of Osama bin Laden, who sought unity with Shiites to counter the West.

IS depicts Shiites as con artists and traitors, often stating that Shiites are originally Jewish tribesmen seeking to infiltrate Islam.

It accuses Shiites of “drowning in worship of the dead” due to their veneration of saints and praying at tombs of imams, and of preferring the 12 revered imams “to the prophets and even to Allah!”

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Viewing Shiite Muslims as deviants of Islam, the group calls on its followers to kill Shiites, using genocidal language in a recent issue of Dabiq.

“Thus the Shiites are idol-worshiping apostates who must be killed wherever they are to be found, until no Shiite walks on the face of earth.”