Half of Syria's population is "food insecure" and nearly a third needs urgent assistance, the UN World Food Programme (WFP) said Monday, as it reported plans to step up aid.
The report came as the International Rescue Committee also warned that Syrians were struggling to secure food as the price of bread has soared by 500 percent since the conflict erupted 33 months ago.
"Recent assessments show that almost half the population inside Syria is food insecure and close to 6.3 million people need urgent, life-saving, food assistance," WFP said in a statement.
Syria's population is estimated at 23 million. Three million have been forced to flee their country ever since a brutal war broke out in March 2011.
The United Nations says food security exists "when all people at all times have access to sufficient, safe, nutritious food to maintain a healthy and active life."
Among the most vulnerable Syrians are millions of people who have been displaced inside the country by the war.
WFP said that in 2014 it plans to feed 4.25 million Syrians displaced internally and around 2.9 million Syrians who fled to Lebanon, Jordan, Turkey, Iraq and Egypt.
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The UN agency said it will also provide nutritional food supplements to 240,000 children aged between 6-23 months to help prevent malnutrition in their early formative years.
"This is the worst humanitarian crisis that we have seen in decades, with every day more vulnerable Syrians pushed into hunger," said WFP Syria emergency coordinator Muhannad Hadi.
Earlier the International Rescue Committee said that four out of five Syrians were worried about food running out, while more than half of them were struggling for access to clean water.
"The price of bread has risen by up to 500 percent," the IRC said in a statement issued as temperatures plummeted to below freezing in parts of Syria.
"Material goods are also in short supply," the non-governmental organisation said in a report based on its surveys of more than 500 communities across Syria.
With temperatures hitting record lows, the cost of blankets at $27 is prohibitively high at around "93 percent of the average monthly income," it added.
The International Rescue Committee also pointed to "severe shortages of basic medical items such as antibiotics, painkillers, and gauze in eight governorates".
The United Nations says more than 9.3 million Syrians are in need of aid.