Thousands of Syrians were stuck in and around Aleppo today as a deal to evacuate people from two Shiah villages in return for Sunni rebels and their families leaving two towns near Damascus halted, a war monitor and activists said.
A auto bomb in northern Syria killed more than 100 people Saturday when it ripped through buses evacuating residents from a besieged government town.
The UK-based Syrian Observatory for Human Rights said the blast was caused by a vehicle bomb.
The Observatory said 2,200 people from Zabadani and Madaya had left, among them 400 rebels. Rebel fighters who were escorting the convoy were also killed.
Those killed in Saturday's attack included civilians and pro-regime fighters who had left their homes in the Idlib province towns of Fua and Kafraya, which had for years been besieged by opposition rebels.
On Friday morning, Madaya's residents said they had boarded the evacuation buses in tears.
Critics say the string of evacuations, which could see some 30,000 people moved across battle lines over the next 60 days, amounts to forced displacement along political and sectarian lines.
They have been touted by the regime as the best way to end the fighting but rebels say they are forced out by siege and bombardment. Russian Federation has alleged that the victims were killed by toxic agents from a rebel chemical arsenal hit by Syrian war planes.
"My home was the most handsome place in Syria, but we leave so no one else has to die here", said one man, speaking on the condition of anonymity to protect relatives who would now fall under government control. Food was distributed after several hours and by early afternoon the evacuees from rebel-held areas were "pressured" to sit back on their buses, Afandar said.
Madaya resident Amjad Al-Maleh, who spoke to AFP on the phone from one of the buses leaving opposition-controlled Madaya and Zabadani at around 6:00 am (0300 GMT), said: "We just left now, around 2,200 persons in around 65 buses".
The Syrian Observatory for Human Rights confirmed the beginning of the evacuation.
In Madaya, residents were given the option to stay and "reconcile" their status with government authorities.
The agreement, hammered out between the two sides on March 30, calls for the evacuation of civilians from four besieged districts of the country: Madaya, Al-Zabadani, Kefraya and Al-Fuaa.
The UN says 4.72 million Syrians are in hard-to-reach areas, including 600,000 people under siege, mostly by the Syrian army, but also by rebels or the ISIS militant group.
Now in charge of all of Syria's major urban centers, Damascus holds the upper hand against rebels in the west of the country and has negotiated a slew of other surrender deals from a position of strength.