Rebel fighters move in a convoy as they head towards the town of Busra al-Harir in Deraa province April 20, 2015.

The leader of a militant Syrian faction that had pledged allegiance to the Islamic State of Iraq and Syria (ISIS) group was killed on Sunday in a suicide attack by rival extremists, a monitoring group said.

“Abu Ali al-Baridi, head of Al-Yarmouk Martyrs Brigade and nicknamed ‘The Uncle’, was killed in a suicide attack by al-Nusra Front,” al-Qaeda’s Syria affiliate, the Syrian Observatory for Human Rights said.

Observatory head Rami Abdel Rahman said Baridi and two of his group’s top leaders were killed in the town of Jamlah in the southern Syrian province of Daraa bordering Jordan.

Baridi’s faction pledged allegiance to ISIS in 2014 and operated in the south of the country, Abdel Rahman said.

Al-Nusra’s official Twitter account confirmed it had attacked Baridi, calling it a “heroic infiltration operation”.

The two factions had been clashing in Daraa “for months”, Abdel Rahman told AFP, adding that al-Nusra fighters fired celebratory gunshots when they learned “The Uncle” had been killed.

At least 32 fighters from al-Nusra, al-Yarmouk Martyrs Brigade and Islamist groups died in intra-rebel clashes earlier this week.

“With this assassination, al-Nusra has asserted its control on the southwestern front of Daraa province, near the border with the (Israeli-occupied) Golan,” Abdel Rahman said.

Daraa province is largely under opposition control and is dominated by the pro-West Southern Front alliance, while the provincial capital is divided between regime and rebel forces.

Al-Nusra and ISIS were originally both part of al-Qaeda’s network in Syria, but ISIS split into its own faction in early 2014 and the groups have been fighting each other ever since.

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