US-backed forces have launched their final assault on the remaining Islamic State (IS) militants in Raqqa.
The Syrian Democratic Forces (SDF) says it began the offensive on Sunday, after a convoy of IS fighters and their families left the city overnight, using civilians as human shields.
No foreign fighters were allowed to join them, and it is unclear how many militants remain in the city.
IS declared Raqqa the de facto capital of its “caliphate” three years ago.
The SDF, an alliance of Kurdish and Arab militias, has been besieging the city for nearly four months.
In a statement released as the battle began, the group said they would not stop “until the whole city is clean of the terrorists who refused to surrender, including the foreign fighters”.
The battle is still anticipated to take some time, with Colonel Ryan Dillon, spokesman for the US-led coalition, saying they “still expect there to be difficult fighting”.
The SDF’s decision to allow some of the militants to leave the city, leaving only a hardcore group of fighters behind, was designed to shorten the fight. It is not known how many remain.
The coalition said “275 local mercenaries and their families” had left Raqqa, according to news agency AP.
Omar Alloush, an official in the Raqqa Civil Council, said about 400 civilians also joined them.
Mostafa Bali, an SDF spokesman, told Reuters they were human shields who the militants refused to release until their own safety was guaranteed.
But the evacuation did not have the full support of their western backers.
Col Dillon said: “We may not always fully agree with our partners at times. But we have to respect their solutions.”
The loss of Raqqa will be seen as another blow for IS, which has been steadily losing ground in both Syria and Iraq over the last two years.
IS, which attracted fighters from across the globe with its extreme interpretation of Islamic law, used beheadings, crucifixions and torture to terrorise residents who opposed its rule.