Updated

Secretary-General Antonio Guterres is again calling on the U.N. Security Council to refer Syria to the International Criminal Court, pointing to "serious violations" including blocking aid deliveries and medical care to millions in need.

He also called on parties to the conflict, all countries, and civil society to cooperate with an independent panel established by the General Assembly in December 2016 to assist the investigation and prosecution of those responsible for war crimes or crimes against humanity in Syria.

Guterres said in a report to the council circulated Friday on the humanitarian situation in Syria in December that "accountability for serious violations is a requirement under international law and central to achieving sustainable peace."

During December, he said, no aid was delivered to over 417,000 people in nine "besieged" locations.