The United Nations warned of a growing risk of mass deaths from starvation among people living in conflict and drought-hit areas of the Horn of Africa, Yemen and Nigeria.

The current crisis could be worse than the 2011 drought in the Horn of Africa that killed more than 260,000 people, the U.N. refugee agency spokesman Adrian Edwards said.

More than 20 million people across Nigeria, South Sudan, Somalia and Yemen, are in areas hit by drought and are experiencing famine or are at high risk of famine, according to UN numbers.