5 million in Mali are hungry - UN
A convergence of droughts, harvest failures, locust invasions and political conflicts in Mali have left 4.75 million people without enough to eat, the UN says.
Officials said close to half a million children will suffer from acute malnutrition by the end of the year.
Unicef emergency director Afshan Khan said malnutrition rates are comparable to the crises in South Sudan and the Horn of Africa.
John Ging, the director of UN humanitarian operations, warned that without additional funds "we can expect that the situation will continue to deteriorate".
The latest figures are worse than Mr Ging's assessment in June that nearly 500,000 children under the age of five were at risk of acute malnutrition and 1.5 million people were "food insecure".
Meanwhile in Kenya, half a million refugees are being forced to go on half rations as the World Food Programme scrambles for funding amid an unprecedented number of major emergencies around the globe.
The UN food agency is increasingly taking this last-resort measure as the world body responds to five humanitarian crises in Syria, Iraq, South Sudan, Central African Republic and now west Africa with the Ebola outbreak, senior spokesman Steve Taravella said.
He added that the WFP expects it will have to reduce rations like this in other places as resources are stretched thin.
"We really don't want to be doing this," he said. "Telling hungry people they'll be receiving less food than they're accustomed to is never easy."
The 500,000 refugees in northern Kenya, most of them from South Sudan and Somalia, will receive a daily food ration of just over 1,000 calories, compared with the 2,100 calories they have been getting, through to the end of January, when a United States food donation is expected to arrive, although that amount is expected to be enough for just six weeks.
The WFP is trying to raise 38 million US dollars (£24 million) to pay for its Kenya refugee operations for the next six months.
This year has seen similar cuts elsewhere, notably in conflict-torn Syria and its neighbours, which have taken in millions of Syrian refugees.
In October, the WFP announced it would have to cut rations for people in Syria by 40%, and this month rations were cut by a further 20%.
While those rations are expected to return to normal in December, the situation for Syrian refugees in the five neighbouring countries is dire, and "we don't know what will happen", Mr Taravella said.
Mr Ging said the United Nations had received just 230 million dollars (£146 million) of the 481 million dollars (£306 million) it needs for humanitarian aid for Mali - just 48%.
Mr Khan said Unicef more than doubled the number of malnourished children it was providing special nutrition for to 120,000 at the end of 2013, "but that is a drop in the bucket compared to what is needed".
Mr Ging and Mr Khan were part of a mission of emergency directors for UN agencies and NGOs that visited Mali from November 3 to 5.
"Mali has been going through a chronic nutrition crisis," Mr Khan said. "It's related to droughts, harvest failures, locust invasions and it's further been aggravated by the political conflict, the insecurity, the population displacement."