Islamic State commander Omar Shishani targeted in US strike in Syria
The US military says it targeted a top commander of so-called Islamic State in an air strike in Syria last week.
An initial assessment suggested Tarkhan Batirashvili, a Georgian known as Omar Shishani, was likely killed along with 12 other militants, officials said.
The strike took place on Friday near the north-eastern town of Shaddadi, where Shishani had reportedly been sent to bolster local IS forces.
There was no immediate confirmation of his death from IS or its supporters.
The US had offered a $5m (£3.5m) reward for Shishani, who it declared a specially designated global terrorist in September 2014.
'Minister of war'
A statement issued by the US defence department late on Tuesday said it was "still assessing the results" of Friday's operation targeting Shishani.
But an unnamed senior defence official told the Associated Press news agency that it was likely the IS military commander was killed. The official said the strike involved multiple waves of manned aircraft and unmanned drones.
Using an acronym based on IS's former name, the defence department said it believed Shishani had been sent to Shaddadi to "bolster Isil fighters following a series of strategic defeats to local forces we are supporting, cutting off Isil operations near the Syria-Iraq border".
Shaddadi was captured last month by the Syrian Arab Coalition, an alliance of Arab rebel groups which have joined forces with the Kurdish YPG militia to battle IS.
A YPG official told the Reuters news agency that it had received information that Shishani was killed but had no details and had been unable to confirm anything.
The defence department said Shishani - which means "Chechen" in Arabic - held numerous top military positions within IS, including "minister of war", and was based in the northern Syrian city of Raqqa, the de facto capital of the so-called caliphate whose formation IS proclaimed in 2014.
"Batirashvili is a battle-tested leader with experience who had led Isil fighters in numerous engagements in Iraq and Syria," it added.
"His potential removal from the battlefield would negatively impact Isil ability to recruit foreign fighters - especially those from Chechnya and the Caucus regions - and degrade Isil's ability to co-ordinate attacks and defence of its strongholds like Raqqa, Syria, and Mosul, Iraq."
Before joining IS in mid-2013, Shishani was the leader of Jaysh al-Muhajirin wa al-Ansar, an al-Qaeda-linked group comprising mostly foreign fighters that fought in the rebellion in Syria.
By late 2013, he had been appointed emir (leader) for northern Syria and was in charge of fighters from Chechnya and elsewhere in the Caucasus.
He was identified as the IS military commander in a video distributed in June 2014.
Shishani is also said to have overseen an IS prison facility in Tabqa, west of Raqqa, where foreign hostages were possibly held, according to the US.