An international aid convoy departed Beirut, Lebanon Monday for three Syrian towns facing food shortages.
Aid is set to be delivered almost simultaneously to the insurgent-held town of Madaya and two towns in the hands of the government, al Foua and Kefraya in Idlib province.
Severe malnutrition among civilians has been reported in all three towns after protracted sieges cut off supplies.
Madaya has been besieged by government-aligned forces since July. The food crisis in the town first sparked an international outcry in late 2015, when residents began posting images online allegedly showing emaciated Madaya children.
Rebels have cited the images as evidence of government human rights abuses, but Syrian state media questions the authenticity of some photos and points to similar crises in towns under siege by rebel fighters.
According to medical aid group Doctors Without Borders, over 250 Madaya residents are suffering acute malnutrition. The aid group has warned that more than 20 people have already starved to death in the town.
Madaya residents are just some of the estimated 400,000 Syrians trapped in besieged settlements across the country. Severe malnutrition has also been reported in the government-held towns al Foua and Kefraya. Both towns are besieged by insurgent groups.
The simultaneous aid deliveries are part of an agreement between international aid groups and the Syrian government.
According to the World Food Programme, the Madaya convoy will arrive first, and will include basic food goods such as rice, cooking oil and flour. A day later similar deliveries will reach al Foua and Kefraya.
If the initial deliveries are successful, medical supplies and winter clothing will be delivered to Madaya by a third convoy, according to the World Food Programme.
These rotating deliveries are expected to continue for a week.
Syria's civil war has left more than 250,000 people dead since the conflict broke out in 2011. Over 11 million Syrians have been displaced by fighting.