BEIRUT (Reuters) - Dozens of busses entered Syria's Islamic State-held Raqqa city overnight, an activist group with sources in Raqqa said on Saturday.
Activist group Raqqa Is Being Slaughtered Silently said on its Facebook page it did not know why busses were there but they had "headed from the northern Raqqa countryside towards Raqqa city last night".
During the more than six-year Syrian conflict, the arrival of busses in a conflict zone has often signaled an evacuation is about to begin.
The U.S.-backed Syrian Democratic Forces (SDF), an alliance of Kurdish and Arab militias, have reached the final stages of a battle to drive surrounded Islamic State militants from their last Raqqa positions.
The SDF could not be immediately reached for comment.
In August, Islamic State fighters agreed to be evacuated from a Lebanon-Syria border area, the first time the militants had publicly agreed to a forced evacuation from territory it held in Syria.
Civilians have been making perilous journeys to escape the Islamic State-held areas as SDF forces advance. The SDF says it helps transport them away from the fighting after they flee.
The offensive to drive Islamic State out of Raqqa, its de facto Syrian capital which it seized in 2014, has long outlasted initial predictions by SDF officials who said ahead of a final assault in June that it could take just weeks.
(Reporting by Lisa Barrington; Editing by Robert Birsel)