(CNN) ISIS continues to bulldoze its way through the cultural heritage of Iraq and Syria, releasing a new propaganda video showing its fighters destroying Iraq's ancient Assyrian city of Nimrud in March.

Nimrud lies close to ISIS' main stronghold in Iraq, the northern city of Mosul.

The video, which ISIS posted Saturday, shows militants attacking the more than 3,000-year-old archaeological site with sledgehammers and power tools before finally using explosives to blow it up.

The United Nations has previously described such deliberate cultural destruction as a "war crime," but in the Nimrud footage the ISIS militants appear proud of their actions.

Here's a roundup of some of the mayhem and destruction ISIS has wrought upon the cultural heritage of Iraq and Syria:

Nimrud

The Iraqi Ministry of Tourism and Antiquities announced in March that ISIS had bulldozed Nimrud.

Photos: Historic sites damaged by ISIS Photos: Historic sites damaged by ISIS ISIS seized control of Palmyra , a UNESCO World Heritage Site dating back 2,000 years, in May, prompting fears for the site's survival. The Syrian government confirmed ISIS fighters have destroyed two Muslim shrines in the ancient oasis city. It's the latest act of cultural vandalism by the Sunni extremists. Hide Caption 1 of 12 Photos: Historic sites damaged by ISIS ISIS released a propaganda video showing its fighters destroying Iraq's ancient Assyrian city of Nimrud in March. The destruction follows other attacks on antiquity carried out by the militant group in Iraq and Syria. The United Nations has described such deliberate cultural destruction as a "war crime." Hide Caption 2 of 12 Photos: Historic sites damaged by ISIS The Iraqi Ministry of Tourism and Antiquities announced in March that ISIS had bulldozed the ruins of Nimrud, seen here in 2009. Hide Caption 3 of 12 Photos: Historic sites damaged by ISIS Bas-relief panels from the Palace of Ashurnasirpal II are seen in Nimrud in 2009. Hide Caption 4 of 12 Photos: Historic sites damaged by ISIS This file photo from 2003 shows the ancient ruins of Hatra in Iraq. It is another one of the cultural sites that have reportedly been damaged by ISIS. Hide Caption 5 of 12 Photos: Historic sites damaged by ISIS Bas-reliefs of masks in Hatra Hide Caption 6 of 12 Photos: Historic sites damaged by ISIS A statue of the goddess Shamiya, or Shahiro, at Hatra in 2009 Hide Caption 7 of 12 Photos: Historic sites damaged by ISIS In this image made from video posted on a social media account affiliated with ISIS, a militant uses a power tool to destroy a winged-bull Assyrian protective deity at the Nineveh Museum in Mosul, Iraq. Hide Caption 8 of 12 Photos: Historic sites damaged by ISIS "It's tragic to see this destruction," said William Webber, from the UK-based Art Loss Register. "Each time you see this you think it can't happen again, but it does." The Mosul museum held 173 original pieces of antiquity and was being readied for reopening when ISIS invaded Mosul in June. Hide Caption 9 of 12 Photos: Historic sites damaged by ISIS An exterior shot of Nineveh in May 2008 Hide Caption 10 of 12 Photos: Historic sites damaged by ISIS Two Parthian Kings of Hatra, seen in the Mosul museum in 2008 Hide Caption 11 of 12 Photos: Historic sites damaged by ISIS In July, a video was released showing the destruction of Jonah's Tomb in Mosul. The tomb was inside a Sunni mosque, seen here in 2008, called the Mosque of the Prophet Yunes (Arabic for Jonah). Hide Caption 12 of 12

"ISIS continues to defy the will of the world and the feelings of humanity," the ministry said then in a statement. "They violated the ancient city of Nimrud and bulldozed its ancient ruins."

At the time, U.S. Secretary of State John Kerry said he was "disturbed" by the reports.

"These depraved acts are an assault on the heritage of the Iraqi and Syrian people by an organization with a bankrupt and toxic ideology," Kerry said in a statement

"The Iraqi government recently nominated Nimrud to be placed on UNESCO's list of world heritage sites. In contrast, (ISIS') twisted goal is clear: to eviscerate a culture and rewrite history in its own brutal image."

Where: Nimrud lies about 30 kilometers (about 19 miles) south of Mosul in northern Iraq.

What: Nimrud was a city in the Assyrian kingdom, which flourished between 900 and 612 B.C.

Why it's significant: UNESCO says Nimrud's "frescoes and works are celebrated around the world and revered in literature and sacred texts."

Mark Altaweel, professor of archaeology at University College London, told CNN's Nic Robertson in March that Nimrud was a large site, the full potential of which had not been uncovered.

As the first Assyrian capital, it accumulated huge amounts of wealth, Altaweel said, and many of the objects found there were very rare and made from highly precious materials.

"I would describe Nimrud as one of the really unique archaeological sites in the entire ancient Near East," he said. "Nimrud is the capital of the first empire in this long series of empires that have profound significance in the way this region develops and ultimately how it affects our own society."

Khorsabad

Iraq's Ministry of Tourism and Antiquities said on March 9 that it had received reports the ancient Assyrian capital of Khorsabad had been destroyed.

"We have warned before and we warn again that those gangs and their sick Takfiri ideology will continue to destroy and steal artifacts as long as there is no strong deterrent," the ministry said in a statement. (A Takfiri is a Muslim who accuses another Muslim of apostasy.)

Where: Khorsabad is about 19 kilometers (12 miles) northeast of Mosul in northeastern Iraq.

What: Assyrian King Sargon II built a palace at Khorsabad between 717 and 706 B.C., Assyrian King Sargon II built a palace at Khorsabad between 717 and 706 B.C., according to the Oriental Institute at Chicago University , which helped excavate the site during the last century.

Khorsabad, one of three cities that served as a capital during the empire's reign, was abandoned after Sargon's death in 705 B.C., the institute said.

Why it's significant: The Oriental Institute says that "Khorsabad is unusual among the Assyrian palaces because of its stylistic innovations, the preservation of paint on its reliefs, and the extensive ancient written documentation concerning the organization of the building project. "

Carved stone reliefs from the site are held in Baghdad, Chicago, Paris and Britain, it said.

Mosul Museum

The razing of Nimrud came a week after a video showed ISIS militants using sledgehammers to obliterate stone sculptures and other centuries-old artifacts in the Mosul Museum.

JUST WATCHED ISIS militants destroy antiquities with sledgehammer Replay More Videos ... MUST WATCH ISIS militants destroy antiquities with sledgehammer 02:01

Where: Mosul is Iraq's second-biggest city, 400 kilometers (249 miles) north of Baghdad.

What: Mosul Museum held 173 original pieces of antiquity and was being readied for reopening when ISIS invaded Mosul in June, Qais Hussain Rashid, the antiquities ministry's director general of Iraqi museums, told Iraqiya TV.

Why it's significant: Mosul Museum is Iraq's second-largest museum. Mosul Museum is Iraq's second-largest museum. Irina Bokova, director-general of UNESCO, said the museum contained large statues from the UNESCO World Heritage site of Hatra as well as artifacts from the archaeological sites of the governorate of Ninevah. The video showed that these had been destroyed or defaced.

"It's tragic to see this destruction," William Webber, from the UK-based Art Loss Register , told CNN. "Each time you see this, you think it can't happen again, but it does. Now other Greco-Roman treasures are at risk around Mosul in Iraq as well as other artifacts in Palmyra and Raqqa in Syria."

Most of the sculptures being destroyed were from the Assyrian period, Webber said.

Mosul Library

On February 27, the U.N. Security Council condemned ISIS' destruction of artifacts in the Mosul Museum as well as the "burning of thousands of books and rare manuscripts from the Mosul Library."

Where: Mosul Library is in the northern Iraqi city controlled by ISIS.

What: The library's collection reportedly included 18th-century manuscripts and Ottoman-era books.

Why it's significant: UNESCO said the burning could be "one of the most devastating acts of destruction of library collections in human history."

UNESCO's Bokova referred to media reports suggesting thousands of books had been burned over several weeks.

"This destruction marks a new phase in the cultural cleansing perpetrated in regions controlled by armed extremists in Iraq," she said in a statement. "It adds to the systematic destruction of heritage and the persecution of minorities that seeks to wipe out the cultural diversity that is the soul of the Iraqi people."

Jonah's tomb

Where: The tomb was inside a Sunni mosque called the Mosque of the Prophet Yunus, which is Arabic for Jonah, in Mosul.

What: The holy site is said to be the burial place of the prophet Jonah, who was swallowed by a whale or great fish in the Islamic and Judeo-Christian traditions. Biblical scholars are divided on whether the tomb in Mosul actually belonged to Jonah. In the Jewish tradition, he returns to his hometown of Gath-Hepher after his mission to Nineveh. And some modern scholars say the Jonah story is more myth than history.

Why it's significant: The story of Jonah is told often in the Christian tradition and has special resonance for that faith, scholars Joel S. Baden and Candida Moss wrote The story of Jonah is told often in the Christian tradition and has special resonance for that faith, scholars Joel S. Baden and Candida Moss wrote in a piece on CNN's Belief Blog

They refer to the destruction of Jonah's tomb as "an attack on both those Christians living in Iraq today and on the rich, if little-known, Christian heritage of the region."

Hatra

"The destruction of Hatra marks a turning point in the appalling strategy of cultural cleansing underway in Iraq," said UNESCO's Bokova and Abdulaziz Othman Altwaijri, director general of the Islamic Educational, Scientific and Cultural Organization, in a joint statement.

Where: Hatra is 110 kilometers (68 miles) southwest of Mosul.

What: Established by the successors of Alexander the Great and dating back to 300 B.C., Hatra became the capital of what some believe to be an early Arab kingdom ruled by the Parthian Empire that also included the fabled city of Petra in Jordan.

Why it's significant: UNESCO says the city withstood attacks by the Roman Empire before falling in the third century to the Persian Sassanid Empire. Hatra is an "excellent example" of a circular fortified city, it says.

"The perfect condition of the double wall in an untouched environment sets it aside as an outstanding example of a series which covers the Parthian, Sassanid and early Islamic civilization. It provides, moreover, exceptional testimony to an entire facet of Assyro-Babylonian civilization subjected to the influence of Greeks, Parthians, Romans and Arabs," its description of the site continues.

Syria

They include the ancient city of Bosra, the eighth-century Great Mosque of Aleppo and the 11th-century Crac des Chevaliers -- a Crusader castle.

Syria has been engulfed in conflict since 2011 when Bashar al-Assad's regime violently suppressed an uprising and opposition rebels took up arms. The situation has deteriorated, drawing in sometimes competing extremist groups, including ISIS.

As the bloodbath continues, it is hard to gauge the level of damage to the country's heritage sites -- both deliberate and collateral.

In March, the United Nations issued a statement saying that Syria's "rich tapestry of cultural heritage is being ripped to shreds."

"World Heritage sites have suffered considerable and sometimes irreversible damage. Four of them are being used for military purposes or have been transformed into battlefields: Palmyra; the Crac des Chevaliers; the Saint Simeon Church in the ancient villages of northern Syria; and Aleppo, including the Aleppo Citadel," it said.

The statement cited alarming reports that Syrian heritage was also being deliberately targeted for ideological reasons.

"All layers of Syrian culture are now under attack -- including pre-Christian, Christian and Islamic," it said.

Why is ISIS destroying archaeological sites?

ISIS is part of a puritanical strain of Islam that considers all religious shrines -- Islamic, Christian, Jewish, etc. -- idolatrous.

In a commentary for CNN, Cornell University archaeologist and classicist Sturt W. Manning wrote that such destruction spoke of "the human folly and senseless violence that drives ISIS."

JUST WATCHED UNESCO chief: ISIS trying to erase world history Replay More Videos ... MUST WATCH UNESCO chief: ISIS trying to erase world history 08:08

"The terror group is destroying the evidence of the great history of Iraq; it has to, as this history attests to a rich alternative to its barbaric nihilism.

"Worse, these acts of destruction supposedly in the name of religion are dishonest and hypocritical: the same ISIS also is busy looting archaeological sites to support its thriving illegal trade in antiquities, causing further incalculable harm," Manning said.

UNESCO's Bokova said in an opinion column for CNN that Iraq's heritage belonged to all its people and its destruction should be considered a war crime.

"The bulldozing of the archaeological site of Nimrud marked a new step in the cultural cleansing underway in Iraq. These acts are a deliberate attack against civilians, minorities, heritage sites and traditions. In the minds of terrorists, murder and destruction of culture are inherently linked," Bokova wrote.

In an interview in March with CNN's Christiane Amanpour, Bokova said it was difficult to assess the extent of the damage done by ISIS without UNESCO experts being on the ground at the sites.

While some of the artifacts damaged in the Mosul Museum were replicas, Bokova said, in Hatra "unfortunately the damage was authentic."