More than 850,000 people in Somalia are in desperate need of food and "in crisis and emergency conditions," the director of UN humanitarian operations said.
John Ging, who just returned from a three-day visit to Somalia, said another 2 million Somalis are considered to be "food insecure".
He told a news conference yesterday: "These figures are very, very large. They tell us a simple message which is that the situation in Somalia for Somalis on the humanitarian side is very grave. It's also very fragile."
Mr Ging said the UN World Food Programme's Food Security and Nutrition Analysis Unit reported this month that 857,000 Somalis are in acute crisis conditions and require urgent humanitarian assistance.
This is "a modest improvement" from the previous six months when 870,000 Somalis desperately needed food, he said.
Somalia has long been a rudderless nation plagued by cyclical drought and famine and decades of armed conflict. Its population is estimated to be about 10 million.
In recent years it has made some strides in security and governance, particularly since August 2011, when al-Shabab militants were forced out of the capital, Mogadishu.
But the al Qaida-linked rebels have not been defeated and the government controls only small parts of the country and is struggling to provide security and battle corruption.
The food security unit said about 75% of the 857,000 Somalis who urgently need food are displaced from their homes, largely as a result of fighting, insecurity and lack of food.
Mr Ging said others are in rural areas that are very hard to access.
"In 2011, we had a global tragedy where 260,000 people died of famine in Somalia," he said.
"We are working very hard to help the people recover in circumstances which are extremely difficult - the climate is very harsh and the security situation equally so."
The United Nations appealed for 933 million US dollars (£560 million) for the humanitarian crisis in Somalia this year, but Mr Ging said so far it has received only 36 million US dollars (£21.5 million) which is "very ominous".
In 2011, the U.N. appeal for Somalia was 86% funded, but last year it was just 50% funded, he said.
"Somalis have suffered endlessly for almost 25 years. We cannot be distracted now from our task to stay with them, to help to consolidate these fragile gains ... and this requires funding," Mr Ging said.
"We need to keep our attention on Somalia. It's incredibly fragile and we don't want a repeat of what happened in 2011."