The top United Nations refugee official said Syrians are about to pass Afghans as the world's biggest refugee population, and that those who have fled the country's crisis "have not escaped their trauma and psychological wounds."
Addressing the U.N. General Assembly on Tuesday, High Commissioner for Refugees Antonio Guterres urged the international community to support Syria's neighbors, who have taken in nearly 2.5 million refugees.
He also highlighted the impact that three years of fighting has had on the youngest Syrians.
"Children who have seen scenes no child should ever see have been wounded physically or psychologically, and with every day the fighting drags on, these children are at risk of losing their future forever," said Guterres.
Secretary-General Ban Ki-moon said large numbers of civilians remain under siege - more than 200,000 by government forces, and 45,000 by opposition fighters. He said both sides must allow humanitarian aid to reach those in need.
"Denying access to people in urgent need of food, water or medical supplies is a fundamental denial of their rights to life and human dignity. Yet there are continued reports of sieges, massacres and atrocities. The international community is strongly committed to pursuing justice and accountability for flagrant violations," said Ban.
In addition to those who have fled the country, the U.N. says at least 6.5 million people are displaced within Syria. The crisis that began in March 2011 has killed well over 100,000 people and wounded nearly 700,000 others.
U.N. human rights chief Navi Pillay said the failure to bring about a comprehensive cease-fire "should weigh heavily on our conscience."
"The international community, led by this assembly, must support an immediate end to one of the most tragic human rights and humanitarian crises of our time," said Pillay.
Pillay's deputy, Kyung-Wha Kang, highlighted the devastation for those still in Syria. She said nearly one-fifth of the country's school have been destroyed or taken over by fighters, 40 percent of hospitals are out of service and the supply of water has been cut in half.
"These numbers grow every day and have become routine news. Perhaps they no longer shock, but they must. It is critical that we remember that behind each number is a family, a child whose life has been ended or devastated," said Kang.
U.N.-Arab League envoy Lakhdar Brahimi brought the Syrian government and opposition together for two rounds of peace talks in the past month, but the negotiations have achieved little. The United States and Russia worked for months to convene the talks, with the hope that the Syrian sides would negotiate an end to the fighting.
Last week, the U.N. Security Council unanimously approved a resolution demanding the government and rebels provide immediate access for humanitarian aid to reach millions in need. It said the humanitarian situation will continue to worsen until there is a genuine political solution that meets the aspirations of the Syrian people.