The transfer has begun of the residents of two Syrian towns in exchange for moving fighters and civilians out of two others, under an evacuation deal reached by rival parties, according to a monitoring group.
The UK-based Syrian Observatory for Human Rights (SOHR) says buses have started transporting people under a pact that involves four towns.
At least 50 buses entered rebel held Zabadani and Madaya near Damascus on Thursday while 100 buses and 20 ambulances arrived in Fouaa and Kefraya in Idlib province.
Zabadani and Madaya have been besieged by the army of Syrian President Bashar al-Assad and fighters of Hezbollah, the Lebanese armed group, since June 2015.
Fouaa and Kefraya are home to mostly Shia Muslims, who have been surrounded by Syrian rebels since March 2014.
An activist in Fouaa who requested to remain anonymous told reporters that rockets targeted some of the buses on their way out, causing damage to one bus and injuring two people.
“There are at least 7,500 people expecting to be evacuated, among them are at least 1,500 rebel fighters,” he said.
Residents leaving Foua and Kefraya will be taken to government-held areas in Aleppo.
The SOHR said at least 2,100 residents, including rebel fighters are to be evacuated from Zabadani and Madaya and transported to Idlib province.
According to the UN, at least 4.7 million people are living in hard to reach and besieged areas in Syria and are exposed to grave protection threats.
In January 2017, the UN said at least 644,000 live in UN-declared besieged locations.
As the Syrian conflict enters its seventh year, more than 465,000 people have been killed in the fighting, more than a million injured and over 12 million Syrians – half the country’s prewar population – have been displaced from their homes