A car bombing blamed on the ISIS group killed at least 26 displaced people in eastern Syria on Friday, the Syrian Observatory for Human Rights monitor said.
The Britain-based Observatory said 12 children were among the victims of the attack on a gathering at a checkpoint run by US-backed fighters in Deir Ezzor province, where the militants are losing ground to two separate offensives aimed at ousting ISIS from Syria.
"Dozens of people were wounded, and the death toll could rise because of the number of serious injuries," said Observatory director Rami Abdel Rahman
The displaced people had been on their way to neighboring Hasakeh province, where camps have been set up to house them in Kurdish-controlled territory, Abdel Rahman said.
ISIS controls roughly one quarter of oil-rich Deir Ezzor province but is battling for survival on two fronts.
One offensive against ISIS is by Syrian regime forces backed by Russian air power, while the second is by a US-backed Kurdish and Arab coalition, the Syrian Democratic Forces.
ISIS fighters are now cornered in part of Deir Ezzor province around the border town of Albu Kamal on the frontier with Iraq, and many civilians have been trying to flee the affected areas.
The militants group seized large areas of both Syria and Iraq in a lightning 2014 campaign, but has this year seen its self-proclaimed "caliphate" crumble as it came under multiple offensives.