"We did not strike in that area", coalition spokesman U.S. Air Force Colonel John Dorrian told Reuters by phone.
But the Iraqi military said the explosion happened as their elite units got to within 50 metres of the mosque as they battled through Mosul's Old City. It was well-known for its 45-meter (148-feet) tall leaning minaret, which was called al-Hadba. The word was spread in a statement from the Iraqi military. The Iraqi military said "ISIS terrorist gangs" blew up the mosque as Iraqi forces were approaching. In February, the Iraqi forces began the operation aimed at liberating western Mosul from Daesh.
Iraqi Prime Minister Haider al-Abadi says the destruction of an ancient mosque in the city of Mosul is "an official declaration of defeat" by so-called Islamic State (IS).
Daesh fighters initially attempted to destroy the minaret in July 2014.
The mosque has been the ideological heart of ISIS in Iraq.
The Iraqis forces took hold of the eastern part of Mosul in January, but the western area, with its winding roads and small buildings, has proved more hard to rest back.
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The U.S. -led coalition is providing air and ground support to the Mosul offensive that started on October 17.
The forces had encircled on Tuesday the group's stronghold in the Old City, the last district under their control in Mosul.
It's hard to overstate the symbolism of the Old City mosque that has witnessed fierce fighting between ISIS militants and coalition forces determined to liberate what was the country's second-largest city.
In Mosul, children are being deliberately targeted and killed by Islamic State militants to punish families and deter them from fleeing, it said.
The Islamic State has blown up The Great Mosque of al-Nuri in western Mosul, according to US and Iraqi forces. The mosque was built in 1172-73, shortly before his death, and housed an Islamic school. Its tilt gave the landmark its popular name: the hunchback.
But residents of Mosul who were incensed with the destruction of their cultural sites protected the mosque in 2014 by forming a human chain around it and creating resistance against IS.
Rasoul described blowing up the two historical Mosul sites "as blowing up the history" and said the group "added another crime against humanity" and world heritage.