A convoy will leave Syria's Raqa on Saturday under an evacuation deal, the US-led coalition said, as a US-backed force battles to seize the Islamic State group's last positions there.

The coalition said the deal reached by local officials aimed to avoid civilian casualties and would exclude foreign IS fighters, but made no mention of whether Syrian jihadists would be able to leave.

"The arrangement is designed to minimise civilian casualties and purportedly excludes foreign Daesh terrorists as people trapped in the city continue to flee the impending fall of Daesh's so-called capital," the coalition said, using the Arabic acronym for IS.

"People departing Raqa under the arrangement are subject to search and screening by Syrian Democratic Forces," it added.

The SDF is the US-backed alliance of Kurdish and Arab fighters that has driven IS from around 90 percent of Raqa since June.

In recent days, talks have been underway on a deal to protect civilians still trapped in the city, and the coalition said the agreement would "save innocent lives and allow Syrian Democratic Forces and the Coalition to focus on defeating Daesh".

The announcement comes after the coalition said earlier Saturday that around 100 IS fighters had surrendered in the city in the last 24 hours.

An SDF military source also earlier told AFP that buses and trucks were waiting outside Raqa to take the surrendered fighters further east to Deir Ezzor province, much of which remains under IS control.

Source: AFP