More than 20 human rights groups issued a joint plea Thursday for the international community to take responsibility for suffering civilians as Syria's war approaches its fifth year.
In a report entitled "Failing Syria", the organisations criticised world powers for not implementing a series of UN Security Council resolutions on the conflict.
Three resolutions adopted in 2014 urged armed actors in Syria to protect non-combatants and aimed to secure greater access to humanitarian aid for millions of Syrians.
"However, the resolutions, and the hope they provided, have rung hollow for Syrian civilians. They have been ignored or undermined by the parties to the conflict, other UN member states and even by members of the (Security Council) itself," the report said.
"Without action by individual governments, the demands within these resolutions remain little more than words on a page."
Last year was the deadliest yet in the conflict, with at least 76,000 people killed out of a total of more than 210,000 since it began on March 15, 2011 with peaceful pro-democracy demonstrations.
Since then, 11.4 million Syrians have fled their homes and nearly four million have left the country in what the UN has called the worst refugee crisis in 20 years.
- 'Betrayal of ideals' -
According to the report, Syria's humanitarian crisis is worsening at an alarming rate. Nearly 10 million people inside the country do not have enough to eat, and more than 11 million are in urgent need of clean water.
"This is a betrayal of our ideals, because we're not supposed to be watching people suffer and die in 2015," said Jan Egeland, secretary general of the Norwegian Refugee Council, which contributed to the report.
The 21 rights groups accused government forces of systematically using rape and sexual harassment as methods of war, and rebel groups of kidnapping women and children for use in prisoner exchanges.
Both regime and opposition forces indiscriminately target civilian infrastructure, including schools and health facilities, they said.
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"I was in class when my school was hit. We ran out of the school right away," said Basma, an eight-year-old Syrian girl quoted in the report.
"I have never seen my school or my friends again. I miss them a lot."
The report, whose signatories included Oxfam, International Rescue Committee, and Save the Children, criticised warring parties in Syria for blocking access for humanitarian organisations to some of the most devastated areas.
It said 4.8 million Syrians live in areas defined by the United Nations as "hard to reach" for aid deliveries -- almost twice as many as in 2013.
- 'Stain on conscience' -
But as needs have increased, funding has not kept pace. Only 57 percent of the money needed to support Syrian civilians and refugees was provided in 2014, down from 71 percent in 2013.
Egeland told AFP that, in the coming year, the UN will need roughly $8.4 billion (7.9 billion euros) in aid for Syrian civilians.
"It's one sixth of the cost of the 2013 Sochi Olympics -- so how could Russia afford the Sochi Olympics, but cannot afford sizeable contributions for this underfunded operation?" he asked.
The report called Syria's humanitarian catastrophe "a stain on the conscience of the international community".
It said UN member states should significantly increase aid contributions and put pressure on warring parties to reach a political solution.
Otherwise, Egeland said, the world could "struggle with the effects of the crisis for two generations to come".
"We're not providing any hope to millions of Syrian youth, so do we then believe they will not be easily attracted to extremism?" he said.
"We hoped it would change a year ago, and we failed. We all failed. Now, in 2015, it can change. It must change."