Almost 1.4 million children suffering from severe malnutrition could die this year from famine in Nigeria, Somalia, South Sudan and Yemen, the UN children's agency said.
In Yemen, where war has been raging for nearly two years, 462,000 children are suffering from acute malnutrition while 450,000 children are severely malnourished in northeast Nigeria.
Fews Net, the famine early warning system, said some remote areas of Nigeria's Borno state are already affected by famine since late last year and the disaster is likely to continue as aid agencies are unable to reach those in need.
Drought in Somalia has left 185,000 children on the brink of famine but that figure is expected to reach 270,000 in the next few months, said UNICEF.
In South Sudan, over 270,000 children are malnourished and a famine has just been declared in parts of Unity State in the north of the country, where 20,000 children live.
UNICEF director Anthony Lake appealed for quick action. "We can still save many lives," he said.
UN Security Council ambassadors are due to travel to northern Nigeria, Cameroon, Chad and Niger next month to draw international attention to the humanitarian crisis triggered by the conflict with Boko Haram militants.