Convoys were to deliver aid to thousands of besieged Syrians Wednesday in what the United Nations has described as a test for the country's warring sides ahead of a hoped-for ceasefire.
The UN announced the planned deliveries late on Tuesday, as its envoy Staffan de Mistura held talks in Damascus aimed at restoring hope for a "cessation of hostilities" world powers want in place by Friday.
Prospects for the ceasefire -- announced by top diplomats in Munich last week -- have been fading as violence continues to shake Syria, including strikes on hospitals on Monday and repeated Turkish shelling of Kurdish militia.
The Syrian Red Crescent said about 100 trucks carrying flour, other food supplies and medicines were to leave for five besieged areas on Wednesday.
About 35 vehicles had arrived at the entrance to Moadimayet al-Sham, a rebel-held town near Damascus encircled by President Bashar al-Assad's forces, an AFP journalist at the scene said.
Another 18 trucks had departed for Fuaa and Kafraya, two Shiite towns in northwestern Idlib province besieged by rebels, the Red Crescent said.
About 50 were to travel to Madaya and Zabadani, two other regime-besieged towns near Damascus.
Almost half a million people in Syria are in areas under siege, according to the UN.
Aid workers say several dozen people have died of starvation just in Madaya, which became a symbol of the plight of besieged Syrians after shocking images of starving residents spread last month.
- 'Duty' to allow aid -
"It is the duty of the government of Syria to want to reach every Syrian person wherever they are and allow the UN to bring humanitarian aid," De Mistura said on Tuesday in Damascus.
"Tomorrow we test this," he said.
A Syrian foreign ministry source rejected talk of a test.
"We don't need anyone to remind us of our duties to our people," the source told the official SANA news agency.
Diplomats have been pressing the ceasefire deal as a step forward in efforts to end the nearly five-year conflict that has left more than 260,000 dead, devastated the country and forced millions from their homes.
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A major international push to resolve the conflict, including Western and Arab nations that have largely backed Syria's opposition and Assad's key supporters Russia and Iran, was launched last year.
But peace talks between the regime and opposition in Geneva quickly collapsed earlier this month and a major regime offensive, backed by Russian air strikes, has continued in northern Aleppo province.
Air strikes on five medical facilities and two schools in northern Syria earlier this week killed at least 50 people, the UN said.
One of the strikes hit a hospital supported by charity Doctors Without Borders (MSF), killing 25 people and prompting widespread condemnation.
MSF did not assign blame for the attack though a Britain-based monitoring group, the Syrian Observatory for Human Rights, said a suspected Russian strike had hit the hospital.
Moscow rejected any responsibility and Syria's UN envoy Bashar al-Jaafari on Tuesday said MSF was responsible because it was not coordinating with the government.
- Turkey warns Kurds -
The situation in Syria has also been complicated by Turkey's launching this week of an assault on Kurdish forces who have been advancing in northern Syria.
Ankara has shelled a Kurdish-led militia which it says is allied with the outlawed Kurdistan Workers' Party (PKK) that has waged an insurgency on its soil for decades.
President Recep Tayyip Erdogan on Wednesday vowed Turkey would never accept the creation of a Kurdish stronghold in northern Syria, saying there was "no question" of Turkey ending its shelling.
"We will not allow a new Qandil on our southern border", Erdogan said in a televised speech, referring to the mountain range in northern Iraq which for years has been stronghold of PKK militants.
Turkey on Tuesday called for foreign ground forces to deploy in Syria, part of a longstanding push by the NATO member for a more robust response to the conflict.
On Wednesday Deputy Prime Minister Yalcin Akdogan told A Haber television Ankara wanted to create a 10-kilometre (six-mile) "safe line" inside Syria that would include the flashpoint town of Azaz near the border.
Turkey has long pressed for a safe zone, backed up by a no-fly zone, inside Syria and has warned Kurdish forces it will not allow them to seize Azaz, which is held by rebel forces.
German Chancellor Angela Merkel on Wednesday also reiterated her call for a no-fly zone to protect civilians, saying the humanitarian situation in Syria was "intolerable".
"If we were able to reach an agreement between anti- and pro-Assad forces on a kind of no-fly zone... then this would save many lives and aid the political process about Syria's future," she told the German parliament.