Two British philanthropists have donated a total of £1.8m ($3m) to help the estimated 12 million people facing starvation in the Horn of Africa.
Hedge fund manager Chris Hohn and Scots tycoon Sir Thomas Hunter say the cash donated by their foundations was "initial support" for the crisis.
The grants will target malnourished children in Somalia and refugees.
The Children's Investment Fund Foundation (Ciff) and Hunter Foundation urged others to come forward with aid.
The Horn of Africa is facing its worst drought for decades, with millions in Ethiopia, Kenya, Somalia and South Sudan in urgent need of food, water and healthcare.
The British public has donated more than £50m since the Disasters Emergency Committee, representing 14 UK aid groups, launched its appeal in July.
The £1.8m from the two philanthropists' foundations - 90% of which came from Ciff - will be distributed to agencies Action for Hunger, Medicins Sans Frontieres, and Concern Worldwide.
Chris Hohn's wife Jamie Cooper-Hohn, who runs the Children's Investment Fund Foundation, said: "Now is the time for philanthropists to come together to act in unison to maximise impacts at this time of crisis for children.
"This is initially a small sum given the magnitude of the challenge but we hope, by this act, to catalyse many others to participate in this effort."
The Hohns have given away hundreds of millions of pounds over the past few years and are thought of as pioneers amongst a new generation of philanthropists.
Sir Tom Hunter, who founded the Hunter Foundation in 1998, added: "Given the scale of the catastrophe in the Horn of Africa we'd implore others to help in any way they can."
A spokesperson for both foundations said: "We believe there is huge scope for far greater collaboration amongst the philanthropic community to fund high impact emergency interventions that demonstrably save lives."
Ciff, a registered charity which helps children living in poverty in developing countries, says there are 16,500 children suffering severe acute malnutrition in Somalia.
The grants aim to immediately target those most at risk and their families.
Ciff and the Hunter Foundation have previously helped build a new maternity hospital in Lilongwe, Malawi.
The United Nations, meanwhile, says around £700m ($1.2bn) of the estimated £1.5bn ($2.5bn) needed to alleviate the disaster has been raised worldwide so far.
The food crisis is said to be the most serious on the continent since the famine in Somalia in 1991-1992, which led to a civil war from which it is yet to emerge.
Five districts in Somalia are suffering from famine, and tens of thousands of Somalis have fled to the capital, Mogadishu and to neighbouring Kenya and Ethiopia.
Some 1,500 Somalis have been arriving every day at Kenya's huge Dadaab camp - the world's largest refugee camp.
The UN said 3.2 million Somalis - almost half the population - were in need of immediate life-saving assistance.