Al-Qaeda's Syrian affiliate confirmed on Wednesday the death of its spokesman Abu Firas al-Suri in a US air strike earlier this week.

In a statement circulated on Twitter, Al-Nusra Front said Suri and other members "were killed during a Crusader (Western) air strike... on April 3, 2016."

It said the raid had hit a training camp, but did not specify where in Syria.

On Monday, the Pentagon said the US military conducted an air raid on an Al-Nusra meeting in northwest Syria the previous day but could not confirm whether Suri had been killed.

Suri was a Syrian national and a "legacy" Al-Qaeda member who fought in Afghanistan in the late 1980s and 1990s, Pentagon press secretary Peter Cook said.

He "worked with Osama bin Laden and other founding Al-Qaeda members to train terrorists and conduct attacks globally," Cook said, adding that Sunday's strike killed several enemy fighters.

Suri's death had been reported by the Britain-based Syrian Observatory for Human Rights, which said that his son and at least 20 other jihadists were also killed Sunday in strikes on positions in Idlib province.