Eight hundred Iraqi refugees returned home from northeast Syria on Thursday and hundreds more are to follow, a Syrian official in the region's Kurdish semi-autonomous administration said.
The Syrian Observatory for Human Rights said the first group left on buses via the Al-Yarubiyah border crossing.
The Iraqi government has "agreed to the return of (a total of) 800 families", the Syrian Kurdish source told AFP, adding that many of them had sought refuge in Syria after ISIS expanded its presence in Iraq.
They had been living in villages bordering Iraq, under the control of the Kurdish-led forces that rule regions of north and northeast Syria.
A senior Iraqi security source said: "We have been checking their identities for security reasons for the past year.
"They've been suffering from the difficult economic conditions in Syria."
Relatives of militants, including children, are held in Kurdish-controlled camps in Syria's northeast, the largest of which is Al-Hol with around 56,000 displaced people and refugees.
Since last year, Iraqi authorities have repatriated hundreds of Iraqi families from Al-Hol.
Terrorist group ISIS ruled large swathes of Iraq between 2014 and 2017.
Kurdish-led forces backed by the United States seized the group's last territorial bastion in Syria in 2019.
