Amaq news agency, which ISIS regularly uses to issue reports, said on Wednesday that Shishani was killed in combat in the town of Shirqat, south of Mosul in Iraq.
Amaq said he died trying to repel forces campaigning to retake the city of Mosul. It did not specify when, but the statement conflicts with US claims made in March.
The Pentagon said in March that Shishani, known as Omar the Chechen, had likely been killed in a US airstrike near the town of al-Shaddadi in the south of the Hasakah province in northeastern Syria.
Officials at the Pentagon said they were aware of Wednesday's report but could not confirm or deny it.
Conflicting reports
However, Rami Abdelrahman, head of the UK-based Syrian Observatory for Human Rights, said Shishani had been wounded in March and died soon after in the countryside east of Raqqah.
“I confirmed from the doctor who went to see him,” said Abdelrahman, adding ISIS likely delayed announcing his death to allow time to line up a successor.
Known for his signature red beard, Shishani is said to have once been a member of an elite Georgian military unit.
The terrorist, whose name was originally Tarkhan Tayumurazovich Batirashvili, was born in Georgia in 1986. He was reportedly fighting alongside Georgian armed forces during the country’s short war against Russia in 2008.
Shishani, who the Pentagon described as Daesh’s “minister of war, ranked among America's most wanted militants under a US program that offered up to $5 million reward on the commander’s head.
Daesh terrorists, who were initially trained by the CIA in Jordan in 2012 to destabilize the Syrian government, now control parts of Syria and its eastern neighbor, Iraq.
In September 2014, the US Treasury Department added Shishani along with 10 other militants to the list of Specially Designated Global Terrorists.
Iraqi forces are advancing towards Mosul, the largest city still under the control of Daesh. They have mostly surrounded Shirqat, 250 km (160 miles) north of Baghdad, and last week retook a major airbase from the militants to use in the main push on Mosul, 60 kilometers further north, Press tv reported.
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