A total of 51 rebels were killed on Thursday during an infighting among rival radical rebel groups in east Syria, the pan-Arab al-Mayadeen TV cited activists as saying.

The so-called Islamic State of Iraq and the Levant (ISIL) seized control over the city of Bukamal in the oil-rich province of Deir al-Zour in eastern Syria, near the Iraqi borders, following clashes with the al-Qaida-linked Nusra Front and so- called Islamic Front, the report said.

The armed militant groups' infighting in Bukamal has killed at least 51 rebels and the death toll is likely to rise, the report said, adding that the Nusra fighters have called up for reinforcement amid intense battles with the ISIL.

The ISIL has recently been fighting against the Nusra Front and the Islamic Front for controlling the Bukamal, which they have captured together from the Syrian government troops before, to control its border point with Iraq's al-Anbar city, which is deemed as one of the ISIL's main strongholds in western Iraq.

The Deir al-Zour province has largely spiraled out of the government control during the country's long-running conflict and recently become a stage for rebels' infighting.

Such infighting has escalated since earlier this year with the focus in northern and eastern Syria, in what observers deemed as a schism that reflected the counter-purposes of the rebel groups and their backers.