A food crisis in Niger is being made worse by hoarders who sell grain at prices beyond the reach of most people, Save the Children says.
The charity warns that the practice is putting the lives of hundreds of thousands of children at risk.
Last week the UN World Food Programme said the West African state was facing the worst food crisis in its history.
After months of drought, floods caused by torrential rains have destroyed crops and drowned farm animals.
Save the Children says unscrupulous traders are buying grain cheaply from farmers as soon as it is harvested.
They then hoard it for several months, waiting until grain runs into short supply.
Farmers are then forced to buy their own crops back at hugely inflated prices. Many cannot afford it and they go hungry, the charity says.
"These traders are using market fluctuations to make a profit at the expense of ordinary people," said Josh Leighton, food security and livelihoods officer at Save the Children.
"They are helping to fuel the current food crisis and are putting hundreds of thousands of children's lives at risk."
The charity says it is working with farmers to find a way for them to store their own grain in community granaries.
The farmers would take out loans to tide them over until food prices increased and then sell their own grain, paying back the loans in the process.
The charity says more than 300,000 children under the age of five in Niger are acutely malnourished, and aid agencies are struggling to feed them.
According to the UN, recent floods have left more than 100,000 people homeless across the country.
The BBC's Thomas Fessy, in Niger's capital Niamey, says cars have been replaced by canoes in some parts of the city.
He says houses along the swollen River Niger have been reduced to piles of clay; crops of mangoes and lemons are underwater, leaving people with nothing to sell at market.