A spokesman for US-backed local forces in Syria says more than a hundred people have been killed in a truck bomb blast in eastern Syria.

Mustafa Bali of the Syrian Democratic Forces (SDF) says the victims were refugees from the war the Islamic State (Isis) group in the region. He said the attack occurred Saturday, 4 November, near the Conoco gas plant near Deir el-Zour city.

Omar Abu Layla of the activist-run DeirEzzor 24 monitoring group said the blast happened at a checkpoint where locals were awaiting passage into SDF territory. He said dozens were killed.

The SDF control several oil and gas fields in eastern Syria, which they seized from IS militants this year.

Britain-based war monitor group, the Syrian Observatory for Human Rights (SOHR), attributed the attack to Isis, according to AFP.

However, the attack was not claimed in IS media.

The bombing occurred days after the Syrian army said it had liberated Deir el-Zour from Isis.

The city had been divided into a government-held and an Isis-held part for nearly three years.

The development is the latest significant defeat for Isis as the militant group sees its self-proclaimed "caliphate" crumble and lose almost all urban strongholds.

In another major blow to the group, SDF forces supported by a US-led coalition recaptured the city of Raqqa from Isis after months of fierce fighting.

Isis seized Raqqa in 2014, making it the Syrian capital of its self-declared caliphate.

Save the Children charity said an estimated 350,000 people, half of whom are children, have fled the recent fighting in Deir Ezzor province.

"The situation in the city, and surrounding countryside, has been especially bleak with civilians trapped between the fighting and all too often caught in the crossfire,"Sonia Khush, Syria director at the charity, told AFP.

Deir Ezzor Syria Islamic State
24 September 2017: People displaced from Deir Ezzor head to refugee camps on the outskirts of Raqqa Bulent Kilic/AFP