Trucks carrying humanitarian aid have begun to enter four of five besieged areas of Syria scheduled for deliveries in a UN-backed deal to deliver help to thousands of trapped residents, an aid agency source and conflict monitor say.
The Syrian government has approved access to seven besieged areas, the United Nations said after crisis talks in Damascus on Tuesday, a week ahead of a planned resumption of peace negotiations between Syria's warring parties.
The United Nations estimates there are 486,700 people in around 15 besieged areas of Syria, and 4.6 million people in hard-to-reach areas.
In some, starvation deaths and severe malnutrition have been reported.
Aid convoys on Wednesday began to enter Madaya and Mouadamiya al-Sham near Damascus which have been under siege by government forces, and the villages of al-Foua and Kefraya in Idlib province which are surrounded by rebel fighters.
Aid has not yet begun to enter Zabadani, also near Damascus and surrounded by government forces, conflict monitor the Syrian Observatory for Human Rights said.
Nine aid trucks crossed a checkpoint to enter Mouadamiya al-Sham earlier on Wednesday, a Syrian Arab Red Crescent source told Reuters.
There have been several aid deliveries to Madaya and Zabadani and to al-Foua and Kefraya this year, but each has to be carefully synchronised between the warring sides so that convoys enter simultaneously.
The Syrian Red Crescent is coordinating with the UN on the deliveries which include wheat and high-energy foods, with medical teams being sent to some areas.
The UN has demanded unhindered access to all besieged areas of the country, where it says hundreds of thousands of people are trapped by fighting and deliberate blockades by various warring sides.
In Madaya, near the border with Lebanon, dozens have starved to death after months of siege by government forces and their allies.
In the city of Deir al-Zor in eastern Syria, parts of which are under siege by Islamic State militants, unverified reports have said up to 20 people have died of starvation.
Deir al-Zor was one of the seven areas to which the aid convoys were expected to head within the next few days, the UN said.
Yacoub El Hillo, UN Humanitarian and Resident Coordinator in Syria, said aid operations must continue beyond recent efforts to restart peace talks, but a solution to the root of the problem must also be found.
Syria's opposition says it will not negotiate with Damascus until sieges imposed by government forces and their allies have been lifted - one of many issues that led to a suspension of the peace talks in Geneva earlier this month.
Talks are scheduled to resume on Feb. 25, but fighting and air strikes continue unabated throughout the country, where 250,000 people have been killed in five years of war.