The United Nations on Thursday said aid convoys were on their way to four Syrian towns but the regime was still refusing aid and blocking medical care for those in need in six besieged towns.
Speaking after hosting a regular meeting of countries involved in the Syrian peace process, UN humanitarian advisor Jan Egeland also said, he hoped to make progress on the release of detainees, especially women, children and sick people. He called on the United States and Russia and other countries to put pressure on the Syrian sides.
As Russia continued on Wednesday to withdraw its military forces from the country, 102 humanitarian organisations signed a joint statement to mark the fifth anniversary of the conflict's beginning and demanded unconditional access to all communities in Syria.
The statement, signed by the UN children's agency UNICEF, Oxfam and others, noted "encouraging signs of progress" in Syria, with the cessation of hostilities, allowing humanitarian agencies to "rush more food and other relief to communities desperate for help".
But access has to go beyond a temporary lifting of sieges and checkpoints, they said.
"Humanitarian access and freedom of movement of civilians in Syria has to be sustained. It has to be unconditional. And it should include access to all people in need by whatever routes necessary," the signatories wrote.
More than 11 million Syrians from a population of nearly 23 million have been forced to leave their homes during the five-year-old conflict, including 4.8 million who have fled the country.
The agencies also warned of an urgent need for a national immunisation campaign for children.
According to Kevin Jenkins, president of World Vision International, there are 13.5 million people in Syria in need of assistance including six million children and many in hard to reach areas.