Almost 1.4 million children are at imminent risk of death this year, as famine looms in Nigeria, Somalia, South Sudan and Yemen, according to the United Nations (UN).

South Sudan's government and three UN agencies on 20 February declared famine in two of the country's counties as a result of a prolonged civil war and an entrenched economic crisis that has devastated the East African nation. More than 270,000 children are severely malnourished in the conflict-ridden nation, according to the UN International Children's Fund (Unicef).

"Time is running out for more than a million children," said Unicef executive director Anthony Lake.

"We can still save many lives. The severe malnutrition and looming famine are largely man-made. Our common humanity demands faster action. We must not repeat the tragedy of the 2011 famine in the Horn of Africa."

In north-east Nigeria, Unicef anticipates some 450,000 children will suffer from severe acute malnutrition this year in the conflict-affected states of Adamawa, Borno and Yobe.

In Somalia, drought conditions are threatening an already fragile population still reeling from decades of conflict. Almost half the population – 6.2 million people – are facing acute food insecurity and in need of humanitarian assistance. This includes some 185,000 children, who are expected to suffer from severe acute malnutrition this year. Unicef suggested this figure is expected to rise to 270,000 in the next few months.

In South Sudan, where famine was declared in parts of Unity State in the northern central part of the country where 20,000 children live, up to 5.5 million could become food insecure at the height of the lean season in July "if nothing is done to curb the severity and spread of the food crisis".

In Yemen, where a conflict has been raging since 2015, 462,000 children are currently suffering from severe acute malnutrition. This is almost a 200% increase since 2014.

Some 2.7 million people in Kenya are also affected by drought and face food insecurity.