Islamic State fighters have released most of the civilians they took with them while retreating from the northern Syrian city of Minbij, the Syrian Observatory for Human Rights told dpa on Saturday.
The civilians were released in Islamic State-controlled territory outside Minbij and near the town of Jarabulus on the border with Turkey, Observatory director Rami Abdel Rahman said.
Kurdish-led forces who gained full control of Minbij on Friday had said that the last remaining jihadis had abducted 2,000 civilians while retreating towards Jarabulus.
The Democratic Forces of Syria (DFS), a US-backed alliance led by the Kurdish People's Protection Units and including fighters from Arab and other ethnicities, declared Minbij "liberated" after a campaign of more than two months.
The capture of Minbij was intended to cut off Islamic State's de facto Syrian capital of al-Raqqa from the often porous Turkish border, the group's last link with the outside world.
Islamic State still holds the town of al-Bab, west of Minbij. Capturing al-Bab would completely cut the group's links with the Turkish border, as well as linking up the main Kurdish-held territory in northern Syria with the enclave of Efrin in the north-west.
But any such move would also be likely to inflame relations between the DFS, rival Syrian opposition forces, and Turkey, which is wary of the Kurds' links with the banned Kurdistan Workers Party (PKK) inside its territory.
Turkish Foreign Minister Mevlut Cavusoglu has said he was given promises by the US that Kurdish forces would not remain in Minbij after Islamic State was ousted.
DFS spokesman Talal Silo, reached for comment on Saturday, would not be drawn on the next target for his forces, who have evicted the militants from swathes of northern Syria over the past 18 months with intensive air support from a US-led coalition.
"Our main goal was always to remove those terrorists from our land," Silo told dpa.
"So any place they are, whether Jarabulus, al-Bab, Deir al-Zour (in eastern Syria) or al-Raqqa - [in] any place they will be our target from now on."
The military commander of the US-led coalition against Islamic State, speaking before the DFS gained full control of Minbij, said the fight there would "set the stage for the eventual attack to seize Raqqa and that will mark the beginning of the end for Daesh [Islamic State] in Syria."
Minbij was " a key line of communication that leads to Raqqa" as well as "a node... for foreign fighter training and facilitation for external operations attacks outside of Iraq and Syria," General Sean MacFarland told reporters on Wednesday.
MacFarland hinted that the Kurdish-led forces might next take the fight to the Islamic State capital, saying the DFS had "gone a long way to assuring us that they can be the defeat mechanism for the enemy in Syria, at least around Raqqa."
They had shown that "they have the wherewithal, the capacity, the will to close with and defeat the enemy in a dense, urban fight," he said.
Meanwhile, the Observatory reported that at least 19 people were killed in over 60 airstrikes by Syrian government and Russian warplanes on Idlib province in the north-west, the main stronghold of the opposition.