Even Iraq's dead Christians aren’t safe from ISIS.

The Islamic State's campaign of terror across the war-torn nation, which has already seen countless beheadings, destruction of priceless art and religious artifacts and insistence that Christians submit or die, now includes mass desecration of graves. Photos of the black-clad, extremist ghouls smashing headstones in cemeteries in the key northern city of Mosul were posted Thursday online under the title "Leveling Graves and Erasing Pagan Symbols."

"The April 16 destruction of Christian graves in Mosul, Iraq by the Islamic State (ISIS) is part of the organization's ongoing campaign against Christianity, in the Middle East and throughout the Muslim world," said Steven Stalinsky, executive director of The Middle East Media Research Institute (MEMRI), which flagged the photos.

The shocking images appeared on the Shomoukh Al-Islam jihadi forum and other various websites, according to MEMRI. They show ISIS militants shattering graves with sledgehammers and carving out the crosses that were engraved on the stones. The photos were released along with a statement claiming to justify the defacing. The "hadith," or Islamic teaching, stated that any grave higher than ground level must be shattered. Any images on such graves must be erased as well, according to the twisted edict.

The hadith claims Prophet Mohammad  told followers not to "leave an elevated grave without leveling it, nor an image without erasing it.”

While desecrating graves is not the worst of ISIS' crimes, Stalinsky told FoxNews.com it sends a strong signal to the West.

“These acts stem from Islamic interpretations that are more broadly held than just within ISIS and these interpretations need to be addressed."

- Ryan Mauro, Clarion Project

"It is important to note that ISIS is documenting its destruction and desecration of Christian sites and its attacks on Christian communities, and on other minorities' sites and communities, and is disseminating these images worldwide via social media," he said. "By doing this, ISIS is not only showcasing what it is doing, but is also mocking the West by demonstrating that it is doing so freely, with no one trying to stop it."

The defacing is just the latest in what some have described as a “cultural cleansing” of Iraq and Syria by ISIS.

“ISIS and other Islamists argue that elevated graves suggest the dead person is closer to Allah than the living, so they must be destroyed,” Ryan Mauro, national security analyst with the Clarion Project, told FoxNews.com. “They believe that grave sites, even ones that aren't elevated, need to be destroyed if they become a place of idolatry in the form of grave worship. Christian ones are especially at risk because Christianity is seen as a form of polytheism.”

Since declaring a caliphate across a vast swath of Iraq and Syria, ISIS has specifically targeted religious institutions-- destroying mosques, temples and churches. They have also destroyed priceless historical artifacts as well as selling other antiquities on the black market to fund their operations.

ISIS also considers worshipping or mourning at grave sites to be equal to idolatry and have often destroyed such sites in an attempt to “purify unbelievers,” Mauro said.

“These acts stem from Islamic interpretations that are more broadly held than just within ISIS and these interpretations need to be addressed,” Mauro said. “More modern Muslims say [the hadith cited by ISIS] was an instruction for a specific time and purpose and is not applicable to today, but ISIS is acting upon a widely-taught interpretation.”

The northern Iraqi City of Mosul has been occupied by ISIS since June 2014 and is considered to be the main stronghold for the terror group in the region. Once ISIS took over the city, it issued an edict to drive out the remaining Christian citizens. As recently as January, the U.S. has begun to coordinate airstrikes with Kurdish forces to take back Mosul. It is believed that a major offense will take place there in the next few months.

Perry Chiaramonte is a reporter for FoxNews.com. Follow him on Twitter at @perrych