The UN special envoy for Somalia, Francois Fall, said conditions in central and southern Somalia were such that 1.7 million people are in dire need of urgent aid to avoid starvation amid what is expected to be the worst harvest in more than a decade.

"I implore everyone concerned to recognize that we are facing a humanitarian challenge of historic dimensions," Fall said in a statement. "We must all pull together if we are to avoid extraordinary suffering and loss of life."

"Time is not on Somalias side. Many communities, especially those in the central and southern regions are already in deep nutritional deficit," he said, noting that malnutrition rates are now above 25 percent in some areas.

"Dams and other watering places are running dry," Fall said. "Crops have failed, rangelands and animal herds are depleted. Measles and other barometers of crisis are taking their toll on the young.

"The international community must move now to avoid a massive loss of life."

The UN Food and Agricultural Organization (FAO) has said as many as 11 million people in four countries in the Horn of Africa -- Djibouti, Ethiopia, Kenya and Somalia -- are on the brink of starvation due to the drought.

But getting relief to Somalia, which has been wracked by anarchy without a functioning central government for 15 years, has been badly complicated by ongoing factional fighting and a surge in piracy off the unpatrolled coast.

"Continued conflict and piracy on the coast have prevented delivery of humanitarian food shipments to Somali ports while rival militia controlling roads and checkpoints demand payment for safe passage," the statement said.

"We must have unimpeded access everywhere and at all times for humanitarian supplies and for those who accompany them," Fall said.

"It is unacceptable that a nation in crisis should be held hostage to bandits demanding tribute from (those) sent to assist," he said, urging immediate donor response to emergency aid appeals.

In late December, Somalia's transitional government appealed for 60 million dollars in aid for some two million southern Somalis facing severe food and water shortages.

It was not clear on Thursday if any donors have thus far responded.

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