Mosul's trademark leaning minaret was missing from its skyline for the first time in centuries Thursday after desperate jihadists blew it up as Iraqi forces advanced on an ancient mosque compound.

Explosions on Wednesday evening levelled the Nuri mosque where Abu Bakr al-Baghdadi gave his first sermon as leader of the Islamic State group and its ancient leaning minaret, known as the "Hadba" (Hunchback).

Officials from Iraq and the US-led anti-IS coalition said the destruction of the site was a sign of the jihadist group's imminent loss of Mosul, with Prime Minister Haider al-Abadi calling it an "official declaration of defeat".

The loss of the unmistakeable 12th century minaret -- one of the country's most recognisable monuments sometimes referred to as Iraq's Tower of Pisa -- left the country in shock.

But the destruction had been widely anticipated, with commanders saying IS, also known as ISIS and Daesh, would not have allowed Iraqi forces to score a hugely symbolic victory by recapturing the site.

"They blew up this place in an attempt to cover up their heavy losses in the media, but the media and the people see the victories and see the collapse of Daesh," Brigadier General Falah Fadel al-Obeidi, from the elite Counter-Terrorism Service, told AFP in Mosul.

IS claimed on its Amaq propaganda agency that the site was hit in a US strike, but the US-led coalition said it was the jihadists who had "destroyed one of Mosul and Iraq's great treasures".

Brett McGurk, the US envoy to the coalition, said it was the "clearest sign yet of desperation and defeat" from the jihadists. 

The destruction of the site in Mosul's Old City adds to a long list of priceless heritage and historical monuments destroyed by IS during its three-year rule over parts of Iraq and Syria.

The minaret, which was completed in 1172 and has been listing for centuries, is featured on Iraq's 10,000-dinar banknote and was the main symbol of Iraq's second city -- giving its name to countless restaurants, companies and even sports clubs in Mosul.

- Mosul battle not over -

After seizing Iraq's Sunni Arab heartland in June 2014, IS reportedly rigged the Hadba with explosives but was prevented from blowing it up by the local population. The jihadists consider the reverence of objects, including of such sites, as heresy.

The minaret used to be visible from many spots in the city, especially from the east bank, across the Tigris river that divides the city.

Iraqi forces had been approaching the Nuri mosque on Wednesday, after launching an assault on Sunday to retake the Old City, the last district of Mosul still under IS control.

About 100,000 residents are believed to still be trapped in the Old City by IS, which has been using civilians as human shields to defend its last redoubt in Mosul.

The area still controlled by the jihadists is small but its narrow streets and the presence of so many civilians has made the operation very perilous.

Two journalists were killed on Monday and two others wounded near the Old City and reports by medics and rights groups suggest that trapped civilians are paying a heavy price.

The jihadists have been offering fierce resistance in the Old City, with barrages of mortar fire and a huge number of booby traps slowing the Iraqi advance.

While Iraqi forces have made good progress to reach the Nuri mosque, Iraqi commanders have warned that the battle for the Old City is far from over.

When asked about the explosions that forever changed the face of the city on Wednesday, one west Mosul resident said that human lives remained more important than any historical monument.

"Although it was Mosul's symbol and icon, there are people who have been killed. They are much more precious than the minaret," 38-year-old Yasser Ali told AFP.

Source: AFP