The UNHCR is warning of an almost ‘inevitable’ humanitarian crisis across at least four north African countries, with 20 million people at risk from mass starvation.

"it's a critical situation that is rapidly unfolding across a large swathe of Africa" Adrian Edwards UNHCR spokesperson

Drought and conflict are the main causes.

The four countries are Nigeria, Somalia, South Sudan and Yemen. Famine has already been declared in South Sudan, and seven million people in parts of Nigeria and the Lake Chad basin alone are suffering from food insecurity.

People are also on the run within their countries due to violence and conflict and greater numbers of South Sudanese refugees are fleeing to Sudan and Uganda, according to one UNHCR official.

Over 4 million #refugees at risk of starvation in Africa and Yemen according to latest from UNHCRhttps://t.co/bdvmWzhT60pic.twitter.com/UzmkQmQKth — USA for UNHCR (@UNRefugeeAgency) April 11, 2017

At the Geneva headquarters of the UN High Commission for refugees spokesman Adrian Edwards said immediate action was required.

“UNHCR reminds the international community that the Horn of Africa drought of 2011 cost more than 260,000 lives, more than half of these children aged below five. A repeat must be avoided at all costs.”

“This really is an absolutely critical situation that is rapidly unfolding across a large swathe of Africa from west to east,” Edwards added.

The UN has scaled up its operations while lamenting a funding shortfall. Some programmes have only between 3 and 11 percent funding.

Overall the organisation has appealed for 4.4 billion dollars (4.1bn euro) but has received less than one billion dollars to date.