Islamic State has destroyed Mosul's al-Nuri mosque and its iconic leaning minaret known as al-Hadba.
Fighters detonated explosives inside the structures on Wednesday night, Iraq's Ministry of Defense says.
Iraqi Prime Minister Haider al-Abadi tweeted early on Thursday that the destruction is an admission by the militants that they are losing the fight for Iraq's second-largest city.
"Daesh's bombing of the al-Hadba minaret and the al-Nuri Mosque is a formal declaration of their defeat," al-Abadi said, using the Arabic acronym for the Islamic State group.
The mosque, which is also known as Mosul's Great Mosque, is where IS leader Abu Bakr al-Baghdadi declared a so-called Islamic caliphate in 2014 shortly after Mosul was overrun by the militants. The minaret that leaned like Italy's Tower of Pisa had stood for more than 840 years.
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An IS statement posted online shortly after the Ministry of Defense reported the mosque's destruction blamed an airstrike by the United States for the loss of the mosque and minaret.
The US-led coalition has rejected the IS claim.
IS fighters initially attempted to destroy the minaret in July 2014. The militants said the structure contradicted their fundamentalist interpretation of Islam, but Mosul residents converged on the area and formed a human chain to protect it. IS has demolished dozens of historic and archaeological sites in and around Mosul, saying they promote idolatry.
