(CNN) The United States and Iraq said ISIS blew up a historic mosque in Mosul that was the ideological heart of the terror group and the birthplace of its self-declared caliphate.
ISIS, through its news agency, said US warplanes were responsible for the loss late Wednesday of the Great Mosque of al-Nuri and its leaning minaret. US officials told CNN the ISIS claim was "1,000% false."
Iraq Prime Minister Haider al-Abadi said the ISIS act amounts to "an official announcement of their defeat." His military commanders said militants blew the mosque up after troops closed in.
The destruction could amount to a war crime, according to the UN Human Rights Council.
"Such intentional destruction is an attack on the religious and cultural heritage of the Iraqi people -- and the whole world," the UN said Friday. "International humanitarian law clearly prohibits such acts, and perpetrators who target these objects while being aware of their religious and historical character may be held accountable for war crimes."
Before-and-after photographs of the destruction.
It's difficult to overstate the symbolic importance of the Old City mosque, whose landmark minaret rose over the city for more than 800 years.
It was during Friday prayers here on July 4, 2014, that ISIS leader Abu Bakr al-Baghdadi declared the founding of a new caliphate and called on fellow Sunnis to carry out a holy war. This was the first and last time the leader of the terrorist group spoke publicly to his followers. The mosque's imam had been executed about a month earlier for refusing to join ISIS, according to the United Nations.
Baghdadi's declaration effectively broke down borders between Syria and Iraq, creating a magnet for foreign fighters wanting to join ISIS' cause. For years, the militant group's black and white flag fluttered from the minaret, a symbol of ISIS' control.
But in recent months western Mosul has witnessed fierce fighting between ISIS militants and coalition forces who are determined to liberate what was the country's second-largest city.
The Islamic complex has been very much on the mind of the Iraqi forces, who believed taking control of the mosque would be a highly symbolic victory. Federal police earlier this year said they looked forward to praying in al-Nuri -- but the resistance continued.
Now the centuries-old mosque complex lies largely in ruins.
Al-Nuri mosque: The irony of ISIS' iconoclasm
Several US officials have told CNN in recent days that US and coalition officials had been observing the mosque in recent days and saw fighters and explosives at the site. The Iraqi military said "ISIS terrorist gangs" blew up the mosque as Iraqi forces were approaching.
Destruction came as troops moved in
The situation in Mosul is desperate. As ISIS is being squeezed into even smaller territory -- a handful of neighborhoods and Mosul's Old City -- the civilians held hostage are running out of food. Residents said ISIS fighters have massacred people, young and old, trying to flee.
The UN children's agency, Unicef, said Thursday that children in west Mosul "are being deliberately targeted and killed to punish families and deter them from fleeing the violence." In less than two months, at least 23 children have been killed and 123 injured in just that part of the city, it said.
About 100,000 civilians remain in the complex battlefield.
Lt. Gen. Abdul Ghani al-Assadi, commander of Iraqi counterterrorism, said Wednesday that he was shocked by the destruction of the mosque but it was not the first time ISIS had targeted Iraq's cultural heritage.
"ISIS had prepared to blow it up, they were only waiting to see how far our forces can reach," he said. "We are no more going to drive them out of the Old City, we are going to kill all of them in the coming days."
Precious monuments lost in Middle East
Once the largest mosques in the world, built in the 9th century on the Tigris River north of Baghdad. The mosque is famous for the Malwiya Tower, a 52-meter minaret with spiraling ramps for worshipers to climb.
The site was bombed in 2005, in an insurgent attack on a NATO position, destroying the top of the minaret and surrounding walls.
Video: ISIS targets historical artifacts
An "oasis in the Syrian desert"
according to UNESCO, this Aramaic city has stood since the second millennium BC and featured some of the most advanced architecture of the period. The site subsequently evolved through Greco-Roman and Persian periods, providing unique historic insight into those cultures. ISIS now controls the ancient city and has
destroyed shrines, temples and monuments.
The most spectacular legacy of Buddhism in the war-torn country, among the tallest standing Buddhas in the world -- the larger at 53 meters, the other 35 -- had survived over 1,500 years since being carved out of sandstone. The Taliban considered the monuments idolatrous and
destroyed them with dynamite.
Yemen's capital city of Sanaa has seen several
suicide bombings for which ISIS claimed responsibility, and air strikes by the Saudi-led coalition -- although it is unclear who is responsible to the latest damage. These have affected both the old fortified city -- inscribed on UNESCO's
World Heritage List since 1986 -- and the archaeological site of the pre-Islamic walled city of Baraqish, causing "severe damage,"
according to UNESCO itself.
Continually inhabited for 2,500 years, and became the capital of the Romans' Arabian empire. The centerpiece is a magnificent Roman theater dating back to the second century that survived intact until the current conflict. Archaeologists have revealed the site is now severely
damaged from mortar shelling.
A world heritage site originally built in 715 by the Umayyad dynasty, ranking it among the oldest mosques in the world. The epic structure evolved through successive eras, gaining its famous minaret in the late 11th century. This was reduced to rubble in the Syrian civil war in 2013, along with serious damage to the walls and courtyard, which historians have described as the worst ever damage to Syrian heritage.
These 20-meter wide water wheels were first documented in the 5th century, representing an ingenious early irrigation system. Seventeen of the wooden norias (a machine for lifting water into an aqueduct) survived to present day and became Hama's primary tourist attraction, noted for their groaning sounds as they turned. Heritage experts
documented several wheels being burned by fighters in 2014.
The fortress spans at least four millennia, from the days of Alexander the Great, through Roman, Mongol, and Ottoman rule. The site has barely changed since the 16th century and is one of Syria's most popular World Heritage sites. The citadel has been used as an army base in recent fighting and several of its historic buildings
have been destroyed.
The covered markets in the Old City are a famous trade center for the region's finest produce, with dedicated sub-souks for fabrics, food, or accessories. The tunnels became the scene of fierce fighting and many of the oldest are
now damaged beyond recognition, which Unesco has
described as a tragedy.
This French-built suspension bridge was a popular pedestrian crossing and vantage point for its views of the Euphrates River. It became a key supply line in a battle for the city, and
collapsed under shelling. Deir Ez-zor's Siyasiyeh Bridge was also destroyed.
The
ancient Assyrian city around Nineveh Province, Iraq was home to countless treasures of the empire, including statues, monuments and jewels. Following the 2003 invasion the site
has been devastated by looting, with many of the stolen pieces finding homes in museums abroad.
The Crusader castle from the 11th century survived centuries of battles and natural disasters, becoming a World Heritage site in 2006 along with the adjacent castle of Qal'at Salah El-Din. The walls were severely damaged by
regime airstrikes and artillery in 2013, and rebels took positions within it.
The purported resting place of biblical prophet Jonah, along with a tooth believed to be from the whale that consumed him. The site dated to the 8th century BC, and was of great importance to Christian and Muslim faiths. It was
entirely blown up by ISIS militants in 2014 as part of their campaign against perceived apostasy.
Among Syria's most famous Ottoman-style mosques, which also shows
Mamluk influence through its light and dark contrasts. The vast site became a hub of the battle for Homs, itself a front-line of the conflict. The sacred mausoleum has
been completely destroyed, and much of the interiors burned.
A key city for the Greeks and Romans, established in 630 BC. Famed as the basis for enduring myths and legends, such as that of the huntress heroine of the same name and bride of Apollo. The ruins were some of the best preserved from that period, but in the wake of Libya's revolution,
vast tracts have been bulldozed including its unique necropolis complex.
Home to one of the world's most impressive collections, with over 100,000 pieces that cover the entirety of Islamic history. The Cairo site was first built in 1881, the museum recently underwent an eight-year multi-million dollar renovation. Shortly after re-opening, a car bomb targeting a nearby police building
caused catastrophic damage and forced the museum to close again.
This 121-year-old wooden building, humble but elegant, was home to the nation's first governor general Muhammed Ali Jinnah for the last phase of his life. The residency
was attacked with rocket fire by a separatist group in 2013, and almost completely demolished. A new structure is being built on the site.
A 15-year civil war of incredible brutality, successive battles with Israel, and sweeping urban development has robbed the 'Paris of the Middle East' of much of its visual lustre. Once known for its landscape of swaggering Ottoman, French and Art Deco architecture, officials say just 400 of 1200 protected historic buildings remain.
Before-and-after photographs of the destruction. The US and ISIS trade blame for
its loss.
American military officials deplored the destruction of the mosque.
"As our Iraqi Security Force partners closed in on the al-Nuri mosque, ISIS destroyed one of Mosul and Iraq's great treasures," said US Maj. Gen. Joseph Martin.
Lt. Gen. Stephen Townsend, the top US commander in the fight against ISIS in Syria and Iraq, said: "I was just in Mosul Wednesday afternoon and close enough to see the mosque and its famous leaning minaret. Little did I know it was for the last time. This is just another example that ISIS is a cruel, heartless and godless ideology that cannot be permitted to exist in this world."
ISIS' obliteration of history
The Special Representative of the UN Secretary-General for Iraq, Jan Kubis, said Thursday that ISIS fighters' destruction of the mosque was a "barbaric act" which "shows their desperation and signals their end."
The United Nations Educational, Scientific and Cultural Organisation's Director-General, Irina Bokova, tweeted that the loss of the mosque was "a cultural (and) human tragedy," adding: "We must protect heritage to protect people."
Bokova also issued a statement deploring the destruction of the ancient structure. "The Al Hadba Minaret and Al Nuree Mosque in Mosul were among the most iconic sites in the city, and stood as a symbol of identity, resilience and belonging.
"When Daesh targeted the mosque and minaret a few month ago, the people of Mosul formed a human chain to protect the site, proving once again that the protection of heritage cannot be delinked from the protection of human lives," she said.
"This new destruction deepens the wounds of a society already affected by an unprecedented humanitarian tragedy, with 3 million internally displaced persons and 6,2 million in need of immediate humanitarian assistance. This calls for immediate and strengthened international mobilization."
ISIS has rampaged through numerous cultural heritage sites in Iraq and Syria in the past three years. The extremist group is part of a puritanical strain of Islam that considers all religious shrines idolatrous.
How ISIS ravaged Palmyra's world treasures
Before: The ruins of the 2,000-year-old Temple of Baalshamin are seen in Palmyra, Syria, in 2007. The ISIS militant group took over the ancient city last year and razed parts of its
World Heritage Site. Syrian government forces recaptured the ancient city from the terror group in March 2016. Click through to see the landmarks before and after ISIS' occupation.
After: A Syrian government soldier walks near what's left of the Temple of Baalshamin on Sunday, March 27. Syrian forces retook the city days before, but damage had already been done by ISIS. UNESCO says it plans to evaluate the extent of
Palmyra's damage soon. Many of the structures -- which date from the first and second centuries and marry Greco-Roman techniques with local traditions and Persian influences -- remain in place, bolstering hopes that ISIS didn't completely raze the world heritage site.
Before: The Arch of Triumph in 2006.
After: The Arch of Triumph on March 27.
Before: The Temple of Bel in 2008.
After: The Temple of Bel on March 27.
Destroyed statues are seen inside the damaged Palmyra Museum on March 27.
Many statues in the museum had their faces chipped off -- in keeping with strict Sharia interpretations of the depiction of human forms.
Before ISIS invaded, authorities took what they could from the museum. But larger items and those fixed to walls had to be left behind.
Destroyed statues inside the Palmyra Museum.
The Syrian directorate-general of antiquities and monuments was positive that the condition of artifacts meant that they could be restored and their "historic value" returned, according to a translation of an article on the
department's website.
ISIS took over Palmyra in May.
By June, ISIS began destroying historical sites.
Damage inside the Palmyra Museum.
Palmyra was a caravan oasis when Romans overtook it in the mid-first century. In the centuries that followed, the area "stood at the crossroads of several civilizations" with its art and architecture mixing Greek, Roman and Persian influences, according to UNESCO.
ISIS fighters earlier this year destroyed part of the historic Roman amphitheater in the ancient Syrian city of Palmyra, according to reports. That followed earlier destruction in the archaeological site.
Fighters also destroyed Iraq's ancient Assyrian city of Nimrud in March 2015.
Earlier that year, militants shoved stone statues off pedestals in the Mosul Museum and took sledgehammers to them and other artifacts. In July 2014, extremists in Mosul also destroyed what was believed to be the tomb of Jonah, a key figure in Christianity, Judaism and Islam.
Iraq's Ministry of Tourism and Antiquities said in 2015 that it had received reports the ancient Assyrian capital of Khorsabad had been destroyed.
CNN's Arwa Damon, Ryan Browne, Nick Paton Walsh, Paul LeBlanc, Jennifer Deaton and Salma Abdelaziz contributed to this report.