The United Nations children's charity has warned almost 1.4 million children are at "imminent risk of death" due to famine across South Sudan, Nigeria, Yemen and Somalia.
The Unicef announcement came a day after a famine was declared in two areas of South Sudan following three years of civil war and severe inflation.
It was the first time in six years a famine had been declared anywhere in the world.
For several months, the aid agency has warned about severe malnutrition affecting north east Nigeria, especially the areas inaccessible because of Boko Haram insurgency.
They estimate almost half a million children will suffer acute food shortages in Borno, Yobi and Adamawa states.
Nearly 500,000 children are also expected to experience "severe acute malnutrition" because of the drought in Somalia and conflict in Yemen.