Al-Qaida's official Syrian wing, the Nusra Front, announced on Thursday the death of its top military commander, who insurgent sources said fell victim to a blast targeting a high-level militant meeting.
General Military Commander Abu Humam al-Shami, a veteran of Islamist militant fighting in Afghanistan, Iraq and Syria, was the group's most senior member to die in the Syrian war, an insurgent source said.
Insurgent sources said a U.S.-led coalition airstrike hit the meeting in the northwestern province of Idlib, but a coalition spokesman said it had not conducted airstrikes in the province during the past 24 hours.
The sources said at least three other Nusra Front commanders also were killed in the blast, which they said hit the town of Salqin, near the border with Turkey.
Syrian insurgents previously have killed rival militants by planting bombs at meetings. The blast comes at a time of flux for the Nusra Front, which is waging war on other insurgents and also looking for support from Gulf states, sources in Nusra have said.
"The Islamic Nation is bleeding because of the news of the martyrdom of Commander Abu Humam," Nusra Front said on Twitter. "It's a major blow to Nusra. A very painful, very powerful hit," one insurgent source said, declining to be named as he was not allowed to speak to the media.
The United States has carried out strikes against one of Nusra's jihadi rivals, Islamic State, in Iraq since July and in Syria since September. It has also targeted Nusra fighters in Syria.
The Nusra Front has also battled western-backed Syrian rebels this year, seizing their territory and forcing them to disarm so as to consolidate its power in northern Syria.
Hazzm, one of the last remnants of non-jihadist opposition to President Bashar al-Assad in northern Syria, dissolved itself last week after weeks of fighting with the Nusra Front.
After Thursday's attack, the Nusra Front told its members not to provide information to the media, the insurgent sources said. The Syrian Observatory for Human Rights, which tracks the conflict, also said that al-Shami was killed, as well as other Nusra Front members.
The weakness of the mainstream Syrian opposition and the growing power of the Nusra Front and Islamic State has complicated diplomatic efforts to end the Syrian conflict that has killed around 200,000 people.
The war started in 2011 after security forces cracked down on a peaceful pro-democracy movement.