Why are millions starving in East Africa?

An internally displaced Somali woman sits with her children outside their family makeshift shelter at their camp in Somalia's capital Mogadishu March 5, 2017. REUTERS

British Olympic champion Mo Farah is supporting a charity appeal, launched on Wednesday, for more than 16 million people facing starvation in East Africa, including Somalia where he was born.

The Disasters Emergency Committee (DEC), an alliance of 13 leading British aid agencies, are raising funds for South Sudan, Somalia, Kenya and Ethiopia, which have been hit by drought.

The United Nations has warned the world faces the largest humanitarian crisis since the end of the second world war with millions in four countries facing starvation and famine.

Here are some the facts about the East African crisis:

* More than 16 million people do not know where their next meal will come from and children risk of dying from starvation.

* Forecasts for upcoming spring rains are poor, which means people will need water, food and emergency aid throughout 2017.

SOUTH SUDAN

* South Sudan is causing Africa's biggest refugee crisis with three million fleeing their homes due to civil war in the world's youngest country.

* More than 100,000 South Sudanese are experiencing famine, with a further one million on the brink of starvation.

* Almost five million people - more than four in 10 of the population - are short of food and water.

* Aid workers have been unable to reach tens of thousands in need due to clashes, denial of access at checkpoints and looting of humanitarian compounds.

SOMALIA

* In war-torn Somalia, more than six million people have no reliable access to food and there are 360,000 acutely malnourished children.

* Experts are warning of an impending famine like the one in 2011, which killed 260,000 people.

ETHIOPIA

* In Ethiopia, 5.6 million people need emergency food aid due to a series of back-to-back droughts and this figure is likely to rise.

* Some 3 million children and pregnant women are projected to be acutely malnourished by May.

KENYA

* In Kenya, some 2.7 million people need food aid due to drought, mostly in the arid north.

* Kenya's government declared a national disaster in February. Sources: Reuters, Britain's Department for International Development, United Nations.