Dozens of wounded opposition fighters, along with members of their families, are being evacuated from a Syrian border town that is besieged by regime forces.
The evacuation was agreed as part of a deal that will, in exchange, see the safe passage of scores of civilians from two villages that are surrounded by opposition in northern Syria.
About 130 people - including 70 fighters - who have been under siege in the town of Zabadani, which is in Syria's south near the Lebanese border, will arrive in Beirut airport on Monday.
They will then fly to Turkey under the supervision of the UN and the International Committee of the Red Cross (ICRC).
Simultaneously, about 450 people - including women and children - were being evacuated from the two Shia villages, Fuaa and Kefraya, which are in Syria's largely opposition-held Idlib.
The opposition contingent and their families will travel to Beirut via the Lebanese border crossing al-Masnaa in convoys of buses. Ambulances also entered Zabadani on Monday to transport the seriously wounded.
They are expected to be transferred to Idlib after they arrive in Turkey.
Sources in Zabadani told Al Jazeera that at least 12 ICRC and UN vehicles had arrived in the town by 8am local time (0500GMT) to take the opposition forces out.
Opposition-held Zabadani has been subjected to a relentless bombardment for months by regime troops, backed by the Shia Lebanese group Hezbollah, in an attempt to take it from the opposition forces.
The evacuation, an effective swap, comes after a negotiated ceasefire deal involving Turkey and the opposition group Ahrar al-Sham on one side, and Iran and the Syrian regime on the other.
Monday’s swap, a rare event in Syria, is considered to be the first phase of a ceasefire deal, brokered in September, to stop the months of fighting in Zabadani.
According to medical sources involved in the operation, the people being transferred from Fuaa and Kefraya have been selected from among those in the village who need urgent treatment.
They are expected to be transported from through the Bab al Hawa border crossing into Turkey. From Turkey, they will travel to Beirut and then on to the Syrian capital Damascus.
"Those who are in urgent need of medical attention will stay in Lebanon until they are able to move again and will then proceed onto Syria," a medical source told Al Jazeera, adding they have been waiting for three months for the deal to be implemented.
The UN in July spoke of "unprecedented levels of destruction and many deaths among the civilian population" in Zabadani caused by barrel bombs dropped by Syrian regime planes.
In October, the Red Cross delivered eight trucks of food and aid to the towns, while simultaneously sending similar trucks to Zabadani and nearby Madaya.
PHOTO CAPTION
Syrian children carry placards as they call for the lifting of the siege off Madaya and Zabadani towns in Syria, in front of the offices of the U.N. headquarters in Beirut, Lebanon December 26, 2015.
Al-Jazeera