The spokesman for Al-Qaeda's Syrian affiliate, Al-Nusra Front, his son and 20 other extremists were killed in air strikes Sunday in the northeast of the country, a monitor said.
"Abu Firas al-Suri, his son and at least 20 members of Al-Nusra and Jund al-Aqsa and fighters from Uzbekistan were killed in strikes on positions in Idlib province," Syrian Observatory for Human Rights chief Rami Abdel Rahman told AFP.
The United States carried out the air strike in Syria that killed the prominent leader of al Qaeda offshoot Nusra Front, U.S. officials told Reuters on Monday, speaking on condition of anonymity.
Opposition sources said Abu Firas, who was a former Syrian army officer discharged in the late 1970s because of his extremist leanings, was a founding member of the militant group and had fought in Afghanistan in the 1980s.
He was a senior member of the al-Nusra Front's policy-making Shura Council.
The United States has targeted al-Nusra Front in the past, although the bulk of the U.S. military's firepower in Syria has been directed at Daesh, which occupies parts of Syria and Iraq.
Abu Firas was a fervent opponent of Daesh'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 U.S. drone strike.
The U.S. 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 Pakistani supporters of the fundamentalist Taliban movement in Afghanistan several decades ago, the rebel sources said.