DAMASCUS — Al-Qaeda’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 senior-most member of the group to die in the Syria war, an insurgent source said.

Insurgent sources said a U.S.-led coalition air strike hit the meeting in the northwestern province of Idlib, but a coalition spokesman said it had not conducted air strikes in the province during the past 24 hours.

The sources said at least three other Nusra Front commanders were also killed in the blast, which they said hit the town of Salqin, near the border with Turkey.

Syrian insurgents have in the past killed member of rival militant groups 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.

Nusra is now considering cutting its ties with al-Qaeda in a rebranding exercise backed by Qatar and some other Gulf states that will bring in more funds, sources say.

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 Nusra.

On Tuesday, Nusra followers published photographs on Twitter of what they said were U.S. weapons, including anti-tank missiles, seized in battles with opposition brigades.

U.S. officials plan to train thousands of Syrian rebels over three years. The program is expected to begin this month in Jordan and focuses on battling the hardline “Islamic State” group rather than Assad.

Hazzm’s collapse has shown how U.S. efforts will prove difficult.

“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.

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.

Insurgents attacked a Syrian government security building in the northern city of Aleppo on Wednesday, bombing it and then launching a ground assault, sources on both sides and a monitoring group said.

The Syrian Observatory for Human Rights said at least 20 members of the security forces and 14 insurgents were killed in the attack on the Air Force Intelligence building.

Jihadist groups including the Nusra Front and the Muhajireen and Ansar army claimed responsibility for the attack, which partly destroyed the building.

The Syrian army said it had “thwarted attempts by terrorist groups to infiltrate the Air Force Intelligence building in Aleppo”. In a statement, the army said it had “eliminated large numbers of terrorists”.

Initial reports suggested the insurgents had set off the bomb in a tunnel dug under or near the building in Aleppo, which has long been a focus of fighting between government and insurgent groups. 

-Reuters, TAAN