The world should be "ashamed" over the humanitarian crisis in Syria where people are starving without medical care, according to the United Nations (UN).
Stephen O'Brien, the UN's under secretary-general for humanitarian affairs and emergency relief, said, despite increased aid deliveries in Syria, people are still starving.
O'Brien demanded unrestricted humanitarian access and told the UN Security Council it must not squander the opportunity presented by peace talks in Geneva.
"The people of Syria cannot afford to see the situation move backward again," he warned. "If the international community fails to maintain momentum politically, with the cessation of hostilities, and with humanitarian access, the situation will only spiral further out of control."
O'Brien criticised the Syrian government's "inhumane" removal of medicine and medical supplies from aid convoys.
He said: "Deliberately deprived of food and medicine, many face the most appalling conditions of desolation, hunger and starvation. We must all be ashamed that this is happening on our watch."
He also warned Syrian president Bashar Assad's government those responsible for the "unnecessary suffering and loss of life" will be held accountable when the fighting stops, saying "there can never be impunity for this behaviour".
According to the UN, the World Food Programme has reached 3.7 million people with food and the World Health Organisation vaccinated over 2.1 million children against polio in March.
The number of humanitarian convoys crossing borders and combat lines has increased, with assistance provided to more than 778,000 people in besieged, hard-to-reach and other priority areas since January.
Also 14 high-altitude air drops since April 10 are helping around 100,000 people in Deir el-Zour.
But O'Brien said: "Current levels of access still leave civilians starving and without medical care."