ISIS blows up landmark Grand al-Nuri Mosque in Mosul where Abu Bakr al-Baghdadi had declared himself "caliph" in 2014

Baghdad: Islamic State militants blew up on Wednesday the Grand al-Nuri Mosque of Mosul and its leaning minaret, an Iraqi military statement said.

Notably, IS leader Abu Bakr al-Baghdadi had declared himself "caliph" in this mosque in 2014.

It was his only public appearance.

The IS blew up the mosque as they prepared to flee the besieged city, Iraqi Joint Operations Command spokesperson Yahya Rasoul told Rudaw TV, that broadcasts from the Kurdish autonomous region in northern Iraq, on Wednesday, Efe news reported.

The jihadists swiftly issued a statement via their Amaq propaganda agency blaming a US strike, but the US-led coalition condemned the destruction as a crime against "the people of Mosul and all of Iraq".

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

"Our forces were advancing toward their targets deep in the Old City and when they got to within 50 metres (yards) of the Nuri mosque, Daesh (IS) committed another historical crime by blowing up the Nuri mosque and the Hadba" mosque, Staff Lieutenant General Abdulamir Yarallah, the overall commander of the Mosul offensive, said in a statement.

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 the jihadist organisation 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 appeared at the Nuri mosque in Mosul, Iraq`s second city, days later to declare himself "caliph" and urge the world`s Muslims to move in.

It remains the last public appearance to date for the jihadist supremo, whose fate and whereabouts are currently unclear and whose "state" has been shrinking for two years.

Iraqi forces on Sunday launched an assault on the Old City of Mosul, eight months into a huge offensive to wrest back the northern city from the jihadists, who had made it their de facto Iraqi capital.

The ancient minaret known as "Al-Hadba" (Hunchback) lies next to the 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 listing 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.

When IS imposed its tyrannic brand of sharia, or Islamic law, in the early stages of its "caliphate", it destroyed several key heritage sites in Mosul, including the main museum and shrines to Jonah and Seth.

It reportedly rigged the "Hadba", which it sees as the subject of a cult that transgresses its own regressive and ultra-conservative brand of Islam, but had been prevented from blowing it up by the local population.

The US-led coalition which carries out daily air strikes and has advisers on the ground supporting the Mosul operation condemned the destruction.

"This is a crime against the people of Mosul and all of Iraq, and is an example of why this brutal organization must be annihilated," said Major General Joseph Martin.

(With Agency inputs)