A U.N.-sponsored deal to evacuate more than 2,000 Islamic State fighters and other militants from rebel-held parts of south Damascus has been delayed, a body that monitors the war said on Saturday, a day after a rebel leader was killed.
Buses were due to transport the fighters to Raqqa, the de facto capital of Islamic State in northern Syria, Lebanese Hezbollah's Manar TV station said.
But the deal fell through after the Army of Islam rebel group's leader Zahran Alloush, through whose territory the convoy had been granted safe passage, was killed in an air strike on Friday, the broadcaster said.
The arrangement was the first of its kind between the Syrian authorities and Islamic State.
It would have marked a significant show of strength by the government of President Bashar al-Assad, increasing its chances of reasserting control over a strategic area 4 kilometers (2.5 miles) south of the center of the capital.
The Syrian Observatory for Human Rights, an independent British-based monitoring group that tracks violence across Syria, said the evacuation had been expected to take place early Saturday but was delayed as there was now no secure territory for the militants to pass through.
Manar TV said buses arrived on Friday to pick up the fighters and at least 1,500 family members but had turned back.
The broadcaster is the official mouthpiece of Hezbollah, a Lebanese Shi'ite group which is a major ally of Assad and has sent its forces to fight alongside government troops.
Islamic State has a large presence in several southern neighborhoods of Damascus, including the Palestinian refugee camp of Yarmouk.
Local hostility towards the Jihadist group - which controls large swathes of territory in Syria and Iraq - has grown.
'A lot of hardship'
"We have had enough with their presence and the fighting that goes and the siege that has caused a lot of hardship," said Yousef, a resident of the nearby neighborhood of Hajar al Aswad, who declined to give his full name for security reasons.
A years-long government siege of parts of Damascus controlled by a patchwork of rebel groups - of which Army of Islam is the largest - has impeded the flow of food and humanitarian aid, starving many people to death in what rights group Amnesty International has described as a war crime.
The United Nations and foreign governments have stepped up efforts to broker local ceasefires and safe-passage agreements toward a wider goal of ending Syria's civil war, in which more than 250,000 people have been killed in nearly five years of fighting.
The U.N. Security Council on Dec. 18 unanimously approved a resolution endorsing an international road map for a Syrian peace process, a rare show of consensus among major powers.
In contrast to other non-Jihadist rebels, Islamic State has been totally opposed to any deal with the Assad government.