Thousands flee as rebel infighting in Syria kills 62.
Meanwhile, talks continued over allowing rebels to leave the besieged Old City in Homs.
Rebels from the al Qaida breakaway group known as the Islamic State of Iraq and the Levant, and fighters of the al Qaida-linked Nusra Front, have fought each other for months over territory they previously captured together from President Bashar Assad's forces.
The rebel-on-rebel violence has raged in the north along the Turkish border that opposition fighters have controlled since a mid-2012 offensive. Earlier this year, it spread to Syria's east, home to most of the country's oil fields.
The Britain-based Syrian Observatory for Human Rights said the rebel infighting took place around three villages in the oil-rich Deir el-Zour province near the Iraqi border. In the past four days 62 rebels have been killed there, the Observatory said.
The rebel infighting has forced tens of thousands to flee the contested villages of Abreeha, Bseera and Sabha, the Observatory said. It gathers information through a network of activists on the ground. Syria's conflict, which began with largely peaceful protests in March 2011, has evolved into a civil war with sectarian overtones that activists say has killed more than 150,000 people.
Islamic extremists, including foreign fighters and Syrian rebels who have taken up hard-line al Qaida-style ideologies, have played an increasingly prominent role, dampening the West's support for the rebellion to overthrow Assad.