IMF chief Rodrigo Rato expressed "deep concern" at reports of dire food shortages by organisations including the UN World Food Program (WFP), which says urgent appeals for aid are going unmet.
"Against this background, I urge the international donor community to respond generously and pro-actively in addressing the food needs of Africa's people," he said in a statement.
The WFP warned on Friday of an impending "humanitarian catastrophe" affecting an estimated 5.4 million people in the drought-hit Horn of Africa countries of Djibouti, Ethiopia, Kenya and Somalia.
The UN agency said they were at imminent risk of starvation and appealed for urgent donations to assist the region's worst-affected populations, which have already been hit by mass livestock deaths.
Mr Rato said other African countries such as Niger, Eritrea and Malawi were also still at risk of food shortages.
He said the IMF was doing its part by advising the African countries on how best to strengthen macroeconomic stability and income growth, and stood ready to extend financial aid.
Kenya’s Information and Communications Minister Mutahi Kagwe announced that the number of Kenyans at risk from the food crisis had increased from 2.5 million to 3.5 million.
The number of districts affected by drought is expected to rise to 37, just over half of Kenya's 70 districts.
In Wajir, in northeast Kenya, malnourished children cried feebly in hospital, too weak to even make themselves heard.
At least 30 people, including 13 children, have already died due to food shortages.
On top of the misery created by hunger at least five cattle herders have been killed in clashes over access to scarce pastures and water, according to the international charity ActionAid.
Maize surplus
The crisis hit as Kenya forecast a surplus harvest of 62,500 tonnes of maize.
Farmers in other parts of the country were waiting in lines for up to two weeks to sell surplus maize, the nation's staple food, to the national cereal and produce board.
Surplus food in the west of Kenya is being exported instead of going to those suffering in other parts of the country.
President Mwai Kibaki's attempts to distribute food aid have been ineffective because of inefficient distribution and monitoring.
The visiting British International Development Secretary Hilary Benn appealed for urgent action.
"We need to act very, very quickly to prevent what is already a problem from becoming a crisis," Ms Benn said after visiting drought-ravaged regions.
“The best way to be sure that food gets to the people who need it is through the World Food Program,” she said.
But Peter Smerdon, spokesman of the World Food Program, said aid agencies do not have money to buy food from districts with surplus harvests.
"WFP is short of US$44 million (A$58.36 million) now to feed 1.1 million people because of the drought," Mr Smerdon said. "Without new donations, WFP will run out of food to distribute in drought affected areas by the end of February."
"Our previous warnings and appeals have sadly received little response from the donors. What is a very limited window of opportunity to avert mass suffering in Kenya is closing very fast. We don't want Kenya to become another Niger," he said.