A Free Syrian Army (FSA) commander has been killed by Islamist militants linked to al-Qaida in Syria.
Kamal Hamami - aka Abu Bassel al-Ladkani, a member of the FSA's supreme military council - was meeting members of the Islamic State of Iraq and the Levant in Latakia to discuss "battle plans" when he was murdered.
FSA spokesman Qassem Saadeddine received a call from the militants saying that they had killed Abu Bassel and "they will kill all the Supreme Military Council".
Al Jazeera reported that the commander was killed after a row in which the local leader of the Islamic State of Iraq and the Levant called the FSA "infidels".
Abu Bassel's brother was also killed at the meeting.
FSA spokesman Louay Megdad said: "We hope that we resort to wisdom rather than fighting as the Syrian revolution will be threatened if the rebels are fighting among themselves."
The FSA was formed in 2011 by army deserters in Turkey and is said to number 40,000 members. Western and Arab countries have backed the moderate units of the FSA in their battle against Assad's forces.
The Obama administration agreed in June to offer "direct military support" to opposition groups.
But many Western countries were concerned about heavy weaponry falling into the hands of radical Islamist groups such as the al-Nusra front. Al-Qaida in Iraq announced in April that it was merging with Nusra to form the Islamic State of Iraq and al-Sham (the Levant).
The leader of al-Qaida, Ayman al-Zawahiri, has urged fighters to strive for an Islamic state in Syria.