Clashes between two extremist factions in north-western Syria have left dozens of fighters dead on both sides and raised fears of more deadly violence between groups battling President Bashar Assad's troops.
The fighting between the al Qaida-led coalition known as the Levant Liberation Committee and the extremist Jund al-Aqsa group left nearly 70 dead in some of the worst clashes between insurgents in years, an opposition monitoring group and a rebel commander said.
The violence, ahead of UN-brokered peace talks later this month, was centred in areas where the central province of Hama and the north-western province of Idlib meet.
A Syrian rebel commander speaking from Turkey said Jund al-Aqsa has proven recently that it is a branch of the Islamic State group that is the arch rival of al Qaida's Fatah al-Sham Front.
The commander said Jund al-Aqsa fighters stormed several areas controlled by the Levant Liberation Committee and killed some of its members, triggering intense fighting.
"There is no solution but to uproot Jund al-Aqsa," the commander said.
The Britain-based Syrian Observatory for Human Rights said the Levant Liberation Committee has captured six villages from Jund al-Aqsa.
The Observatory said two days of fighting has left 69 fighters dead, including 39 from the Levant Liberation Committee. It said the 30 dead from Jund al-Aqsa include four suicide attackers who blew up their vehicles.
Abdul-Rahim Attoun, a senior al Qaida religious official in Syria, blamed Jund al-Aqsa for being a group that paid allegiance to IS. He added that Jund al-Aqsa was blocking roads used by the Levant Liberation Committee to attack government forces.
A Jund al-Aqsa commander who goes by the name of Karmo said the fighting was triggered by Levant Liberation Committee attacks on Jund al-Aqsa positions.
In the southern city of Daraa, where clashes between insurgents and government forces have continued for days, opposition activist Ahmad al-Masalmeh said an air raid had hit a hospital, putting it out of service.
The fighting came as a state-run newspaper said in an editorial that a meeting between the Syrian government and opposition in Kazakhstan this week will not be "fruitful" unless they are focused on fighting terrorism.
The two-day conference in Astana that begins on Wednesday is aimed at strengthening a December 30 ceasefire. The government has long referred to all those fighting against it, including mainstream rebels, as "terrorists".