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).
Mosul - 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.
Aerial photographs show the complex largely destroyed.
The mosque, which was more than 800 years old, was where in July 2014 IS leader Abu Bakr al-Baghdadi demanded allegiance in his first and only public appearance following the declaration days earlier of a "caliphate".
The mosques destruction has brought widespread condemnation.
A senior US commander in Iraq said IS had destroyed "one of Mosul and Iraqs great treasures".
"This is a crime against the people of Mosul and all of Iraq, and is an example of why this brutal organisation must be annihilated," Maj Gen Joseph Martin said.
What happened to the Great Mosque?
The Iraqi commander in charge of the offensive to retake Mosul said troops were within 50m (160ft) of the mosque when IS "committed another historical crime".
Footage released by the Iraqi forces shows the ancient landmark being demolished.
Previous reports said IS had rigged the mosque with explosives to stop the advance of Iraqi troops, but that local residents had until now prevented the militants from blowing it up.
IS says the mosque was destroyed by a US air strike but has not provided any evidence to support this.
Iraqi forces are one street away from entering the mosque site, according to state TV, and more details may emerge if they do so.
Is the battle for Mosul over?
Thousands of Iraqi security forces, Kurdish Peshmerga fighters, Sunni Arab tribesmen and Shia militiamen, supported by US-led coalition warplanes and military advisers, have been involved in the battle to retake the key city since 17 October last year.
The government announced the full "liberation" of eastern Mosul in January, but the west of the city has presented a more difficult challenge, with its narrow, winding streets.