Syria's civil war has forced more than nine million people from their homes, creating the world's largest displaced population, the UN said on Friday, describing the continuing conflict as "unconscionable".
"It is unconscionable that a humanitarian catastrophe of this scale is unfolding before our eyes with no meaningful progress to stop the bloodshed," UN refugee chief Antonio Guterres said in a statement.
With more than 2.5 million Syrians currently registered or awaiting registration as refugees in neighbouring countries, Syrians are expected to soon overtake Afghans as the world's largest refugee population.
In addition, more than 6.5 million people have been displaced inside the country.
The total number of people who have fled their homes in Syria now exceeds 40 percent of the war-ravaged nation's pre-conflict population, UNHCR said, stressing that at least half of all those displaced are children.
"No effort should be spared to forge peace. And no effort spared to ease the suffering of the innocent people caught up in the conflict and forced from their homes, communities, jobs and schools," Guterres insisted.
The conflict, which began with a brutal government crackdown on protests in March 2011, is estimated to have killed more than 140,000 people.
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The impact on the surrounding region has also been devastating.
The number of refugees in Lebanon alone is approaching one million and predicted to swell to as many as 1.6 million by the end of the year.
"Lebanon already has the highest per-capita concentration of refugees of any country in recent history," UNHCR said, pointing out that there were now nearly 230 registered Syrian refugees for every 1,000 Lebanese.
That would be equivalent to nearly 19 million refugees in Germany or more than 73 million in the United States, the agency said.
Some 584,000 Syrian refugees have also flooded into Jordan, while 634,000 are in Turkey and 226,000 in Iraq, according to UN figures.
"Imagine the crushing social and economic consequences of this crisis on Lebanon and other countries in the region," Guterres said, calling for "much stronger international support."
Fewer than four percent of fleeing Syrians have so far sought safety in Europe, excluding Turkey, he said. But he cautioned that Syrians were increasingly taking life-threatening risks to reach the continent illegally.
"What kind of a world is this where Syrians fleeing this violent conflict have to risk their lives to reach safety, and when they finally make it, they are not welcomed even turned away at borders?" he said.
UNHCR has called Europe, North America and the Asia-Pacific to make 30,000 resettlement places available to Syrian refugees this year and another 100,000 in 2015 and 2016.