A deal to evacuate four besieged Syrian towns began on Wednesday with an exchange of prisoners between rebels and government forces, local sources and state media said.
Thousands of people had been expected to leave government-held Fuaa and Kafraya and opposition-controlled Madaya and Zabadani on Wednesday, but sources told AFP that evacuations were likely to start at dawn the following day.
The exit of civilians and fighters from the four besieged towns come under an agreement brokered by rebel backer Qatar and government ally Iran last month.
An AFP photographer in government-held Aleppo city saw 12 prisoners released by the opposition, nine of whom appeared to be suffering injuries, arriving along with eight bodies.
Syrian state news agency SANA said the four children and eight women had been transferred with the bodies of "eight martyrs" from "terrorist groups in Idlib province".
It said the exchange of prisoners marked the start of the "implementation of the first phase of the agreement".
SANA said that "19 militants" were transferred from Fuaa and Kafraya at the same time.
A source in the jihadist Tahrir al-Sham alliance confirmed the exchange.
Fuaa and Kafraya are government-held Shiite-majority villages in the otherwise rebel-controlled province of Idlib.
Madaya and Zabadani are opposition enclaves surrounded by regime forces in Damascus province.
The exchange marks the beginning of the implementation of the deal to evacuate the four towns, as well as part of the Yarmuk Palestinian camp in southern Damascus.
Negotiators and residents said buses had entered Madaya and Zabadani on Wednesday morning, but that people were heading back home after hearing of the delay.
"The implementation of the four towns agreement has been delayed until Thursday morning," government negotiator Hassan Sharaf told AFP, without specifying a reason.
- 'Back home' after delay -
Another government coordinator for the negotiations, Mohammad Taqiddin, earlier said vehicles had yet to arrive at Fuaa and Kafraya, and blamed rebel groups for delaying the agreement.
"The entry of buses into Zabadani and Madaya was a goodwill gesture from the government but they will not leave without a simultaneous exit of the Fuaa and Kafraya convoy," Taqiddin said.
Madaya resident Amjad al-Maleh said he had not eaten since Tuesday "because the trip (to Idlib) takes about 20 hours and the buses don't stop" for restroom breaks.
"I'm back home now and I'll try to sleep. The deal has been delayed until tomorrow morning but I don't think it will happen before Sunday," Maleh told AFP.
More than 30,000 people are expected to be evacuated under the deal, which was postponed after objections from both sides and tensions following a suspected chemical weapons attack on a rebel-held town in Idlib province.
All 16,000 residents of Fuaa and Kafraya are expected to leave, heading to government-held Aleppo, the coastal province of Latakia or Damascus.
Civilian residents of Madaya and Zabadani will reportedly be allowed to remain if they choose. Those who leave, along with rebels, will head to opposition territory in Idlib.
The four towns are part of an existing agreement reached in 2015 that requires aid deliveries and evacuations to be carried out to all areas simultaneously.
But access has been limited, with food and medical shortages causing malnutrition, illness and even death among besieged residents.
The UN says 4.72 million Syrians are in so-called hard-to-reach areas, including 600,000 people under siege, mostly by the Syrian army, but also by rebels or the Islamic State group.
More than 320,000 people have been killed in Syria since the conflict began in March 2011 with anti-government protests.