The Islamic State (IS) shared photos of the destruction of Christian relics on Twitter on Monday, increasing calls for the terrorist group to be stopped.
Pictures of smashed crosses, statues and other ancient items destroyed in Nineveh led to condemnation from across the globe.
"They don't care what it's called," Middle East Media Research Institute Executive Director Steven Stalinsky said of the destruction. "They are just following their ideology and that means getting rid of churches and minorities. It is the Islamic State, and there's no room for anyone else.
"This has been going on for some time, a systematic campaign to rid the region [of Christianity]," he continued.
The extremists have persecuted, raped and killed Christians and Shiite Muslims across the Middle East. Christian churches and Shiite shrines have been bombed, and homes and historically significant sites destroyed in Iraq and Syria.
Last week, three ancient cities were destroyed using army equipment, and the militants demolished artifacts that were thousands of years old.
"We cannot remain silent," Irina Bokova, leader of the United Nations Educational, Scientific and Cultural Organisation, said after the ancient city of Nimrud was levelled. "The deliberate destruction of cultural heritage constitutes a war crime.
"I call on all political and religious leaders in the region to stand up and remind everyone that there is absolutely no political or religious justification for the destruction of humanity's cultural heritage."
The Mosul Public Library was blown up last month, destroying more than 10,000 books and 700 rare manuscripts. Civilians allegedly gathered what books they could in flour sacks, but those caught hoarding books were threatened with death.
A University of Mosul professor reported that other cultural institutions have been targeted by IS since December, including the Sunni Muslim library, the library of the Latin Church and Monastery of the Dominican Fathers, and the Mosul Museum Library.