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. <br/><br/>Iraqi forces say IS blew up the Great Mosque of al-Nuri and its famous leaning minaret as jihadists battled to stop advancing pro-government troops. IS said American aircraft had destroyed the complex, a claim denied by the US.<br/><br/>The mosque, which was more than 800 years old, was where in July 2014 IS leader Abu Bakr al-Baghdadi commanded allegiance in his first and only public appearance following IS' declaration days earlier of a caliphate. The mosque's destruction has brought widespread condemnation.