Video shows the moment the minaret of Mosul's Grand al-Nuri Mosque was blown up

The short clip, which was released by the Joint Operation Command, shows the medieval mosque being destroyed in what appears to be a controlled detonation after being rigged with explosives.

It shows the 45-metre minaret collapsing vertically into a plume of dust, as a man laments in the background, "Oh God."

The Iraqi military has said that the Islamic State group blew up the mosque's leaning minaret and main building as its troops closed in on the jihadists in their final stronghold of the country's second city.

The extremists, however, have blamed a US strike on the collapse, but the US-led coalition condemned the destruction as a crime against "the people of Mosul and all of Iraq".

An Iraqi military source told The New Arab on Friday that Counter Terrorism units and Federal Police have advanced deeper into the Old City and that fighting was focused around the compound of the al-Nuri mosque.

Iraqi Prime Minister Haider al-Abadi said the destruction of the sites was "an official declaration of defeat" from IS in the eight-month-old battle for Mosul.

Iraqi troops had been around 50 meters away from the mosque, when IS detonated it, the source added.

Security sources said late on Wednesday that tens of civilians were trapped under the rubble of the destroyed mosque.

Iraqi Prime Minister Haider al-Abadi said the destruction of the sites was "an official declaration of defeat" from IS in the eight-month-old battle for Mosul.

The destruction of two of Mosul's best-known landmarks comes on the fourth day of an Iraqi offensive backed by the US-led coalition to take the Old City, where holdout jihadists are making a bloody last stand.

It adds to a long list of Iraqi heritage sites and monuments IS has destroyed in Iraq and Syria since Baghdadi created his "caliphate" straddling both countries, almost exactly three years ago.

IS proclaimed its self-styled "caliphate" in June 2014, after sweeping across Iraq's Sunni Arab heartland, an unprecedented experiment in jihadist statehood.

The Iraq-born Baghdadi made a rare appearance at the al-Nuri mosque in Mosul days later to declare himself "caliph" and urge the world's Muslims to move in.

The ancient minaret known as "Al-Hadba" (Hunchback) lies next to the al-Nuri mosque and was the most loved and recognisable landmark in Mosul, sometimes referred to as Iraq's Tower of Pisa.

The "Hadba" was completed in 1172 and had distinctive ornamental bands of brickwork wrapping around its cylindrical shaft.

It started tilting centuries ago and has long been considered an endangered monument.

The minaret, with its unmistakeable shape, was the symbol of the city and featured in many local shops signs and advertisements. It gave its name to countless restaurants, companies and sports clubs.