Nearly a quarter of Yemen's population of 22 million need emergency food assistance, the World Food Programme announced on Wednesday.
A WFP food security survey indicates that "almost one quarter of the Yemeni population needs emergency food assistance now," said Lubna Alaman, the UN agency Yemen representative, in a statement received by AFP.
"Hunger is on the increase in Yemen and rising food prices combined with conflict are taking their toll on many families," she added.
According to the survey, "22 percent of the population -- some five million people -- are experiencing severe food insecurity."
"This is nearly double the level of severe food insecurity measured in 2009, and above the threshold at which external food assistance is normally required," the statement said.
"A further five million people are moderately food insecure, and at risk of becoming severely food insecure in the face of rising food and fuel prices and conflict," it added.
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WFP says it has increased its humanitarian assistance in 2012 to feed 3.6 million people affected by rising prices and the conflicts across the country that are estimated to have displaced around 670,000 Yemenis.
The survey's final report, which comes out next month, will include details on malnutrition rates in Yemen, which the statement described as "alarming."
In Hudaydah province, on Yemen's west coast, "acute malnutrition rates are the worst in the country at an estimated 28 percent," it said, well above the World Health Organisation's emergency threshold of 15 percent.
The survey was conducted in November and December last year, interviewing almost 8,000 households in 19 out of 21 governorates.
UN agencies warned in December that Yemen is on its way to becoming another Somalia, saying nearly four million people will be affected in 2012 by the the impoverished nation's political and economic turmoil.
Deadly anti-regime protests swept Yemen last year, finally forcing president Ali Abdullah Saleh to step down in February after 33 years in power.
The political crisis has left the country's economy in tatters and aggravated the dire security situation, with Al-Qaeda militants launching a wave of attacks in the mostly lawless south since Saleh's departure.