A senior official from Syria's main opposition group says a fragile international attempt to halt nearly five years of fighting is in danger of total collapse because of attacks by government forces.
The cessation of hostilities drawn up by Washington and Moscow faced "complete nullification" because Syrian government attacks were violating the agreement, the official of the Saudi-backed opposition High Negotiations Committee said on Monday.
France said there were reports of attacks on opposition forces in breach of the deal, which came into force on Saturday, and countries backing the Syrian peace process met to try to clarify the situation.
UN Secretary-General Ban Ki-moon said the pause in the fighting was largely holding, despite some incidents that he hoped would be contained.
The Kremlin said the process was underway, although it had always been clear it would not be easy.
In Washington, the White House said the United States remained committed to implementing the cessation of hostilities despite reports of violations over the weekend.
The British-based Syrian Observatory for Human Rights said the cessation was largely holding with casualties greatly reduced compared with before the agreement took effect.
The cessation of hostilities, the first of its kind since the war began in 2011, is a less formal arrangement than a ceasefire. It is meant to allow peace talks to resume and aid to reach besieged communities.
Aid trucks carrying non-food items such as blankets on Monday entered Mouadamiya, a suburb of Damascus under siege by government forces, the Syrian Arab Red Crescent said.
The United Nations and other agencies hope to deliver aid to more than 150,000 people in besieged areas over the next five days.
Countries belonging to the International Syria Support Group, led by the United States and Russia, met in Geneva on Monday.
They are supposed to monitor compliance with the deal and act rapidly to end any flare-ups.
"We have received indications that attacks, including by air, have been continuing against zones controlled by the moderate opposition," French Foreign Minister Jean-Marc Ayrault said in Geneva.
"All this needs to be verified."
