The U.S. military carried out an airstrike Sunday on “a senior Al Qaeda operational meeting in northwest Syria” that resulted in “several enemy killed,” including a prominent leader in the jihadist group’s Syrian offshoot, known as the Nusra Front, according to the Pentagon.

Echoing Pentagon press secretary Peter Cook, the U.K.-based Syrian Observatory for Human Rights (SOHR), which uses a network of ground sources to track the conflict in Syria, reported that Abu Firas al-Souri, a high-level spokesman for the Nusra Front, was killed in the attack. The airstrike took place in Syria’s rebel-held northwestern province of Idlib.

The Observatory added that al-Souri’s son and “at least 20 members” of the Nusra Front, Jund al-Aqsa, and extremists from “other factions of Uzbek nationalities” were also killed in the U.S. attack.

Jund al-Aqsa is a jihadist group that fights alongside the Nusra Front.

Cook said the United States believes “al-Souri was in that meeting and we are working to confirm his death.”

According to the SITE Intelligence Group, which monitors jihadi activity online, al-Souri was killed in the airstrike, adding that it targeted the headquarters of Jund al-Aqsa.

Citing Syrian rebel sources, Reuters reports that the strike appeared to be carried out by a U.S. drone, a claim that the Pentagon declined to confirm.

“Al-Souri is a Syrian national and a legacy al-Qaeda member. He fought in Afghanistan in the ’80s and ’90s and worked with Osama bin Laden and other founding al-Qaeda members to train terrorists and conduct attacks globally,” the Pentagon press secretary told reporters.

Reuters learned from “Islamist rebel sources” that al-Souri “was a founding member” of al-Qaeda “and was a senior member of its policy-making Shura Council.”

The sources added that al-Souri worked with bin Laden in encouraging support among Pakistanis for the Taliban movement in Afghanistan several decades ago.

Reuters reports:

They added that Abu Firas, who was a former Syrian army officer discharged in the late 1970s because of his Islamist leanings, played a significant role in training Muslim Sunni jihadists who came from many parts of the Arab world to Afghanistan to fight the Russian occupation of the country.

The rebel sources reportedly added that al-Souri “had many followers within the hardline group and gave commentaries released by Nusra Front on issues ranging from governance to religious jurisprudence.”

Cook stressed that the United States continues to target the Nusra Front as an al-Qaeda affiliate in Syria.

“In this instance, we’re talking about a historic al-Qaeda member who may be affiliated with al-Nusra. Now, al-Nusra has been an affiliate of al-Qaeda, so it’s in very much one in the same,” Cook said.

“We targeted … someone who was present, who has had a history in higher leadership of al-Qaeda dating back to Afghanistan, and so we will await to see what the results of that strike were and whether or not he was removed from the battlefield,” he added.

For over a month, a fragile ceasefire has held up in Syria as the various parties attempt to negotiate an end to Syria’s civil war, which started in March 2011.

The “cessation of hostilities” excludes Islamic State (ISIS/ISIL) and the Nusra Front.

“Air and land attacks by Syrian and allied forces continue in parts of Syria where the government says the groups are present,” notes Reuters.

Syrian dictator Bashar al-Assad and his allies, which include Russia and Iran, consider all opposition groups to be terrorists.