Around 60,000 people have fled towns in Deir Ezzor province of eastern Syria that have been the scene of fierce clashes between rival jihadists, the Syrian Observatory for Human Rights said Saturday.

The battle between al-Qaida affiliate Al-Nusra Front and the breakaway Islamic State of Iraq and the Levant (ISIL) has raged for four days despite an order from al-Qaida chief Ayman al-Zawahiri to stop fighting.

"Residents of the towns of Busayra, home to 35,000 people, Abriha, home to 12,000 people, and Al-Zir, home to 15,000 people, have nearly all been displaced by the fighting in the area," said the Britain-based monitoring group.

The monitoring group, which relies on a vast network of contacts on the ground for its data, said Al-Nusra Front's fighters burnt down several houses in Busayra, as did ISIL in Abriha.

At least 62 fighters have been killed in this week's clashes, said the Observatory.

The latest showdown between Al-Nusra and ISIL erupted on Wednesday in energy-rich Deir Ezzor, bordering Iraq.

"There are battles now in an area around 10 kilometers (six miles) from Busayra that has an oil rig and a gas plant," said Observatory director Rami Abdel Rahman.

The group said hundreds of the displaced had reached Turkey but the vast majority sought refuge in other rebel-held areas of Deir Ezzor province.

Conflict in Syria since March 2011 has killed more than 150,000 people and forced nearly half the country's population to flee their homes.

Al-Nusra Front is seen by many rebels as an ally, but ISIL has been widely rejected by the armed opposition to President Bashar Assad's regime because of its quest for hegemony and abuses.

Mainstream rebel fighters launched a massive offensive against ISIL in January and Al-Nusra Front joined the battle later.