US officials on Tuesday called on other countries to sharply increase aid to famine and drought-hit east Africa, warning that the needs of the starving outstrip the pace of assistance.

US officials made the appeal after returning from a visit to Kenya with Jill Biden, wife of Vice President Joe Biden, which included a tour of refugee camps and meetings with top government figures.

Gayle Smith, a special assistant to President Barack Obama, said the United States was already the lead donor, having contributed 560 million dollars, including 105 million dollars announced Monday.

"We will continue to support the relief effort," Smith said in a conference call with journalists.

"But we are also aggressively reaching out to other countries, because this is of a scale that we certainly can't do it alone. We need other countries to step up with us."

Smith said the "biggest need quite frankly now is for cash contributions."

Such funds enable UN agencies and non-government organizations "to provide whatever may be needed the most effectively, whether it is food, whether it is therapeutic feeding, whether it's access to water," she added.

Former Tennessee Senator Bill Frist warned that "in spite of the US stepping up and the world stepping up, the demands and the needs are growing even faster than what is being provided" to help victims of the famine.

Frist, a Republican, said his participation in the tour pointed up the bipartisan effort that is needed to fight famine at a time when Democrats and Republicans squabble over how to deal with the worsening US economy.

Many people do not realize, especially in a troubled economic environment, that "this is the most acute food security emergency anywhere in the world, now and in recent years," Frist said.

The United Nations last month declared famine in two areas of southern Somalia, as the world slowly mobilized to help 12 million people battling hunger in the region's worst drought in 60 years.

Tens of thousands of people have already died and parts of Kenya, Uganda, Ethiopia and Djibouti are also hit by drought.

Thousands of Somalis fleeing the famine have poured into Kenya and Ethiopia, compounding the problems faced by those two nations.

Around 12.4 million people in the region currently face acute food shortages and 3.2 million in Somalia need "immediate lifesaving assistance," the UN said.

earlier related report
Mogadishu residents flee Somali rebel clashes
Mogadishu (AFP) Aug 8, 2011 - Residents fled from pockets of violence around Mogadishu Monday, two days after a surprise rebel pullback that had led the government to claim it fully controlled the famine-stricken city.

Fighting erupted in several areas in the south and north of the city, as African Union-backed government troops set up bases in former Shebab strongholds.

"We are very worried, and many people have already fled to stay away from the firing," said Abdulahi Duale, a resident from the famine-stricken capital's northern Suqaholaha district.

"We could hear shooting close to our neighbourhood," he added.

The Al-Qaeda-affiliated rebels who had controlled around half of Mogadishu abandoned their positions in a surprise withdrawal on Saturday but some units remained active on the outskirts of the capital.

Another resident, Huda Ali said: "We could hear the heavy fighting on Sunday night. We are planning to flee because there are stray bullets reaching close to us now."

Government officials celebrated the hardline rebel pullout, but the Shebab say it is merely "a change of military tactics."

"It was the second day of our changed tactics, and the mujahedeen fighters carried out at least five attacks," Shebab spokesman Abdulaziz Abu Musab told reporters.

"We have inflicted heavy losses on the enemy... where the Christian invading forces tried to expand," he added.

Government forces dismissed the rebel claims, reporting only sporadic shooting as soldiers moved cautiously into former Shebab-held areas.

"Our forces are making a gradual advancement into areas of the city where the Islamist militants have left," said Abdikarin Dhegobadan, a senior government officer.

"There is no resistance we are encountering so far -- the very few rebels remaining are running away, and just firing shots from far away," he added.

Yusuf Mohamed Siad Indhoade, the leader of a pro-government militia, said the Shebab were forced to withdraw from Mogadishu because of internal wrangles.

"The tactic change they are claiming is nonsense. We know they are very weak because of the internal disputes and they could not stand a large offensive the government was planning against them, so they pulled out before it was too late," he told reporters.

The city was quieter on Monday morning after fighting during the night, but residents continued to move out, fearing further conflict.

About 100,000 people from drought-stricken areas have come to Mogadishu over the past two months in search of food, water and shelter, and aid efforts to reach them continued Monday.

The UN refugee agency (UNHCR) airlifted urgent supplies into the city, the group's first such operation in five years.

Relief items are normally delivered by road or sea, but the "unprecedented rise" in civilians fleeing famine forced the agency to airlift supplies to save time, it said.

The 31-metric-tonne delivery, the first of three flights due in coming days, included 2,500 kits containing plastic sheeting for shelter, sleeping mats and blankets, as well as water and cooking utensils.

"This airlift of emergency assistance items will allow us to continue delivering aid to those displaced by drought and famine," UNHCR Somalia representative Bruno Geddo said in a statement.

The United Nations has officially declared famine for the first time this century in Somalia, including in Mogadishu and in four southern Somali regions, and warned that it could spread.

Much of southern Somalia -- including the majority of regions declared to be in famine -- is still controlled by the Shebab rebels.

Somalia is "the most severe humanitarian crisis in the world today and Africa's worst food security crisis since Somalia's 1991-92 famine," the United Nations has warned.

The United States was expected to announce $105 million in fresh aid to the region, in a pledge due to coincide with a visit to Kenya's Dadaab refugee camp by Jill Biden, wife of US Vice President Joe Biden.

Some $2.4 billion are required to assist 12 million people in the region but only around half of that amount has been received.

Parts of Ethiopia, Djibouti, Kenya and Uganda have also been hit by the Horn of Africa's worst drought in decades.