Acute child malnutrition in parts of Zimbabwe has increased by almost two-thirds compared with last year, according to aid agency Save the Children.
In a new report, the agency said "some children are wasting away from lack of food".
It said there was a shortage of 18,000 tonnes of food needed for January, and urged world donors to increase aid.
Programme director for Save the Children in Zimbabwe, Lynn Walker, told the BBC some five million people or about 50% of the country's population were now in need of food aid.
As well as suffering economic meltdown, Zimbabwe is experiencing a cholera outbreak.
President Mugabe has blamed the West for his country's problems.