The attack came as Syrian Forces presses an offensive against ISIS in the town of Tabqa as part of an assault on the extremist bastion Raqqa.
The dawn ISIS attack hit a makeshift camp where some 300 families were waiting to cross into government-held territory in Hasakeh province, in northeastern Syria.
"At least five suicide attackers blew themselves up outside and inside a camp for Iraqi refugees and displaced Syrians in Hasakeh province," said Rami Abdel Rahman, the head of the Syrian Observatory for Human Rights activist group.
Heavy clashes then erupted between the ISIS terrorists and the SDF, some of whose combatants were among the dead, Abdel Rahman told AFP.
The makeshift camp lies in the Rajm al-Salibeh area just inside Syrian territory, and at least 21 of the dead were displaced Syrians or Iraqi refugees, the Observatory said.
"At least 30 people were wounded, and the death toll may rise because some people are in critical condition and others are still unaccounted for," the Britain-based activist group said.
Kamal Derbas, a press officer for the Kurdish Red Crescent, put the civilian death toll at 22.
He told AFP the attack began at 4:00 am local time (0100 GMT) and that 35 people were wounded.
"The dead will be buried in Al-Hol," he said, referring to the nearest town.
