Abu Firas al-Suri the voice of the al Qaeda affiliated militant group that also is known as Jabhat al Nusra, died Sunday, the London-based Syrian Observatory for Human Rights, or SOHR, said.
Suri was killed alongside his son and at least 20 other al-Nusra fighters, northwest of Idlib in northwestern Syria, SOHR reported.
It was unclear whether Syrian or Russian aircraft launched the strike, it said.
Al Nusra released a video in March 2014 detailing Suri's life, the SITE Intelligence Group said.
Suri was born in the Damascus countryside in 1949, graduating military college in 1970, according to SITE's translation of the video.
However, he was discharged in part because of his religious beliefs and went on to carry out operations against the Alawite Assad regime, eventually emigrating to Afghanistan and training jihadists there, it said.
According to the video, Suri first returned to Syria in 2013 to try to help mend a rift between then al Qaeda affiliates al Nusra and ISIS.
Al Qaeda offshoot
Al Nusra developed during the 5-year civil war in Syria as an offshoot of al Qaeda.
Like ISIS, it is trying to establish an Islamic state, though primarily in Syria.
Al Qaeda originally gave its backing to ISIS as well as al Nusra, but distanced itself from ISIS early 2014.
The move followed months of infighting between the groups and an attempt by ISIS to absorb al Nusra under its leadership; al Qaeda had reportedly asked ISIS to withdraw from Syria.
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Threat to U.S.
The report by the Institute for the Study of War and American Enterprise Institute criticized the White House's ISIS-centric strategy.
"Any strategy that leaves Jabhat al Nusra in place will fail to secure the American homeland," the authors wrote. "Al Nusra is quietly intertwining itself with the Syrian population and Syrian opposition. ... They are waiting in the wings to pick up the mantle of global jihad once ISIS falls."
According to a U.S. official, Suri was targeted because of an importance he had that went well beyond his duties as a spokesman for al Nusra, which has sought to reconstitute a strong leadership base in Syria in the form of a Shura Council. Suri was the chairman of that council, the official said. The council is designed to improve communications and solidify global support for al Qaeda ideology. Suri was critical to this reconstitution, the official said.
ISIS leadership also dented
ISIS has also suffered leadership losses in recent weeks.
Many analysts considered Qaduli to be the group's second-in-command.
"We are systematically eliminating ISIL's Cabinet," Defense Secretary Ash Carter said
, adding it was "the second senior ISIL leader we've successfully targeted this month."
The Pentagon said officials had also confirmed the death of ISIS' "minister of war," Abu Omar al-Shishani.