The international Red Cross is appealing for $400 million to help millions of people facing famine or the risk of it in four conflict-ridden countries — Somalia, Yemen, South Sudan and Nigeria.

The Geneva-based humanitarian agency said Wednesday it wants a "massive scale-up" in assistance and hopes to provide "essential aid" to about 5 million people.

Operations Director Dominik Stillhart said 20 million people facing starvation "is not something we are dealing with every day."

Stillhart urged those involved in fighting to abide by norms of warfare, and said "no amount of aid money will overcome political obstructionism."

While South Sudan is facing famine, Stillhart said Yemen and Somalia face a three- to four-month "window" before it could set in, and that 300,000 people face acute malnutrition in northeast Nigeria.