Fighting between rival jihadist groups in eastern Syria killed 74 people on Monday, AFP reported, citing the Syrian Observatory for Human Rights.
The clashes between Al-Qaeda’s Syrian branch Al-Nusra Front and the Islamic State of Iraq and Syria (ISIS) have prompted 60,000 people to flee towns in the oil-rich province.
The Observatory said 69 fighters on both sides had been killed in the clashes on Monday, along with five civilians.
The deaths bring to 150 the toll since the latest confrontation between the groups erupted last week in Deir Ezzor, bordering Iraq.
Powerful jihadist rebel groups in Syria, including the Islamic Front and Al-Nusra Front, have been locked in fierce fighting with ISIS since January.
The fighting broke out after allegations that ISIS brutally abused civilians and other opposition fighters battling to topple the regime of Syrian President Bashar Al-Assad.
Tensions were further exacerbated when Al-Nusra and other rebel factions accused ISIS of killing Islamist Front commander Abu Khaled al-Suri in a suicide car bomb attack in February.
The latest clashes come even after Al-Qaeda leader Ayman al-Zawahiri ordered the Al-Nusra Front to halt fighting against ISIS.
In an audiotape posted online last Friday, Zawahiri addressed Al-Nusra Front head Abu Mohammed al-Jolani directly, and ordered that "all soldiers of the front immediately cease fighting" rival Islamist groups.
Instead, he urged Jolani to "devote himself to combat the enemies of Islam, specifically Baathists, Shiites and their allies" - a reference to the Baathist regime of Syrian President Bashar al-Assad.
Previously, Zawahiri said that inter-rebel fighting amounted to “sedition”. In late January, Zawahiri issued a similar message, in which he urged all jihadist groups and “every free person in Syria seeking to overthrow Al-Assad... to seek an end to fighting between brothers in jihad and Islam immediately.”
The fighting between Al-Nusra and ISIS has killed around 4,000 people, the Britain-based Observatory told AFP.