Urgent action is needed to stop drought in West Africa's Sahel region turning into a humanitarian disaster affecting 13 million people, Oxfam says.
The charity says the international community waited too long to respond to famine in East Africa last year.
Oxfam has launched a £23m ($36m) emergency appeal to help reach more than a million of the most vulnerable.
A BBC correspondent says refugees fleeing fighting in northern Mali are adding to the problem.
Launching its appeal, Oxfam said that malnutrition rates across Chad, Burkina Faso, Mali, Mauritania, Niger and northern Senegal are hovering between 10% and 15%, and in some areas have risen beyond the emergency threshold level of 15%.
It says that more than one million children in the Sahel region are at risk of severe malnutrition.
In parts of Chad, Oxfam says, some villagers are digging up ant hills to gather grain that the ants have stored.
The agency says that drought, high food prices, severe poverty and regional conflict are causing the crisis.
"Millions of people are on the threshold of a major crisis," said Mamadou Biteye, Oxfam Regional Director for West Africa.