The Syrian army carried out an operation that killed the military commander of the al Qaeda-linked Nusra Front on Thursday in northwestern Syria, Syrian state media reported.
Abu Humam al-Shami was killed by an explosion during a meeting of Nusra Front leaders in Idlib province. Insurgent sources said at least three other Nusra Front commanders were killed in the blast.
The Syrian state news agency SANA, quoting its correspondent, said Abu Humam and a number of other Nusra leaders had been killed in an army operation targeting the meeting held in the village of Hobait in a rural area of Idlib.
Insurgent sources said the targeted meeting had been held in Salqin, some 100 km (60 miles) to the north of Hobait.
The Syrian Observatory for Human Rights, an organisation that tracks the war, said there was conflicting information on where Abu Humam had been killed.
SANA also cited a military source saying the army had carried out "concentrated strikes" against Nusra and other Islamist groups in the Abu al-Dhuhur area, which lies to the northeast of Hobait.
Insurgent sources initially said the US-led alliance had killed Abu Humam in an air strike. But a coalition spokesman said it had not conducted air strikes in the province during the past 24 hours.
The Nusra Front has expanded its hold over Idlib province in recent months, seizing territory from mainstream Syrian rebel groups that have received Western backing.
Leaders of the Nusra Front are considering cutting their links with al Qaeda to form a new entity backed by some Gulf states trying to topple President Bashar al-Assad, sources have said.