Washington: The United States has carried out an air strike in Syria that killed a prominent leader of Al Qaeda offshoot Nusra Front, Abu Firas Al Suri, US officials told Reuters on Monday.
Rebel sources said Abu Firas, who was a former Syrian army officer discharged in the late 1970s, was a founding member of the militant group and had fought in Afghanistan in the 1980s.
He was a senior member of Nusra Front's policy-making Shura Council.
The United States has targeted Nusra Front in the past, although the bulk of the US military's firepower in Syria has been directed at IS militant group, which occupies parts of Syria and Iraq.
Abu Firas was a fervent opponent of IS's style and was ideologically at odds with the militant group.
The Syrian Observatory for Human Rights, which tracks violence in the country, had said he was killed in a suspected Syrian or Russian air raid on a village northwest of the city of Idlib in northwestern Syria on Sunday.
But rebel sources said the attack appeared to have the hallmarks of a US drone strike.
The US officials, who spoke on condition of anonymity, declined to offer details on the strike itself, including whether it was carried out by manned or unmanned aircraft.
They also did not say whether the Nusra Front leader was specifically targeted.
The Pentagon did not immediately respond to requests for comment.
From Madaya, near Damascus, Abu Firas worked with Al Qaeda leader Osama bin Laden in galvanizing support among supporters of the fundamentalist Taliban movement in Afghanistan several decades ago, the rebel sources said.
Meanwhile, An Iranian military official said that Iran has sent commandos to Syria as advisers.
"We are sending commandos from army's Brigade 65 and other units to Syria as advisers," General Ali Arasteh, deputy chief liaison of the army's ground force, was quoted as saying by the Tasnim news agency.
Arasteh said last month that Iran at some point might decide to use commandos and snipers from its regular armed forces as military advisers in Iraq and Syria.
A fragile "cessation of hostilities" has held in Syria for over a month as the various parties try to negotiate an end to Syria's five-year-old civil war.
But the truce excludes IS and Nusra Front, and air and land attacks by Syrian and allied forces continue in parts of Syria where the government says the groups are present.