The Islamic State (IS) militant group has confirmed the death of its top leader Abu Bakr al-Baghdadi, a local news website reported on Tuesday.

"Daesh organization (IS group) circulated a brief statement through its media in the (IS-held) town of Tal Afar in the west of Mosul, confirming the killing of its leader al-Baghdadi without giving further details," Iraqi news agency al-Sumaria News said on its website.

"Daesh said in its statement that the name a new caliph (Islamic top leader) will be announced soon, calling on the (IS) militants to continue their steadfastness in the redoubts of the caliphate and not being dragged behind the sedition," al-Sumaria said, citing an anonymous source from Nineveh Province.

"The announcement caused widespread uproar among supporters of the organization," the website said.

The news report came a day after Iraqi Prime Minister Haider al-Abadi formally declared Mosul liberated from IS after nearly nine months of fierce fighting to dislodge the extremist militants from their last major stronghold in Iraq.

"I declare to the whole world the end, failure and collapse of Daesh state, the state of IS group terrorism, which they announced it here in Mosul three years ago," Abadi said in a speech in Mosul.

On Oct. 17, 2016, Abadi announced the start of a major offensive to retake Mosul, the second largest city in Iraq.

Mosul, 400 km north of Iraq's capital Baghdad, came under IS control in June 2014, when government forces abandoned their weapons and fled, enabling IS militants to take control of parts of Iraq's northern and western regions.