"The Karkh criminal court in Baghdad sentenced to death by hanging one of the most prominent leaders of IS, who served as a deputy of Baghdadi," judicial spokesman Abdel Sattar Bayraqdar said.

The Iraqi authorities announced in February that Ismail Alwan Salman al-Ithawi had been extradited from Turkey after fleeing first Iraq and then Syria as the group's self-proclaimed "caliphate" crumbled.

The jihadist was tracked and detained through cooperation between Turkish, Iraqi and US intelligence agencies, a senior Iraqi official told AFP at the time.

He said the arrest came after an elite Iraqi unit hunting IS members "infiltrated the highest levels" of the jihadist group, which has claimed a string of deadly attacks in the West in recent years.

A native of the Iraqi city of Ramadi, Ithawi was accused of holding several positions including IS "minister" in charge of religious edicts.

Originally from Iraq, Baghdadi has been dubbed the "most wanted man on the planet" and the United States is offering a $25 million reward for his capture.

He has been pronounced dead on several occasions, but an Iraqi intelligence official said in May that he remained alive in Syrian territory by the Iraqi border.

In a purported new audio recording released last month, the IS chief called on Muslims to wage "jihad" .

He made his only known public appearance in Iraq's second city of Mosul in July 2014.

Iraq has condemned several hundred people, including around 100 foreign women, to death for IS links, and dozens of convicted jihadists have already been executed.

Many more have been handed life terms, including nine Tajik women who were sentenced by an Iraqi criminal court on Wednesday for belonging to IS, a judicial official said.

The country has repeatedly faced criticism from international human rights groups over the high number of death sentences handed down by its anti-terrorist courts.

Iraq declared "victory" over IS in December after a three-year war against the jihadists who once controlled nearly one third of the country as well as swathes of neighbouring Syria.

The Iraqi military has kept up operations targeting mostly remote desert areas where jihadists have continued to carry out attacks.

Over the border in Syria, US-backed fighters last week launched a fierce assault against a dwindling pocket of territory held by IS in eastern Deir Ezzor province.