In Niger, which the United Nations classifies as the world's least developed country, starving families are eating flour mixed with wild leaves and boiled plants.
More than 7 million people – almost half the population – currently face food insecurity in the country, making it the hardest hit by the crisis.
According to UN agencies, 200,000 children need treatment for malnutrition in Niger alone.
"Niger is at crisis point now and we need to act quickly before this crisis becomes a full-blown humanitarian disaster," said Caroline Gluck, an Oxfam representative in the country.
With food prices spiralling, people are being forced to slaughter malnourished livestock, traditionally the only form of income.
Drought-stricken Niger has been struck by devastating flooding, aid agencies have said.
Crop failure combined with a severe drought had already thrust tens of thousands of people into a perilous state in Niger and neighbouring Chad in the Sahel region of central North Africa.
But now severe flooding is making the situation even worse, Save the Children said today.
Heavy rainfall since the end of July has inundated six regions of Niger, affecting more than 58,000 people.
Houses have collapsed and rotting animal carcasses are contaminating flood water, spreading disease, the agency said.
The region of Zinder in the south of the country has been hit hardest, with 28,000 people affected.
More than 37,000 animals have drowned in the floodwaters.