US-backed Kurdish forces in Syria say they are resuming their campaign against Islamic State militants who still control areas near the border with Iraq.

Lelwa Abdullah, a spokeswoman for the Kurdish-led Syrian Democratic Forces in the eastern Deir el-Zour province, announces the final phase of the operation against IS in the area has begun.

She said the SDF will "liberate those areas and secure the Syrian-Iraqi border and end the Daesh presence in Syria once and for all."

The SDF had redeployed hundreds of its forces to western Syria after Turkish troops attacked the Kurdish-held Afrin enclave earlier this year, effectively putting operations against IS on hold.

An array of Syrian and Iraqi forces has driven IS from nearly all the territory it once held in the two countries.