The civil war in South Sudan has forced more than two million children to flee their homes, two UN agencies said today.

Children make up 62 percent of the more than 1.8 million South Sudanese refugees who have arrived mainly in Uganda, Kenya, Ethiopia and Sudan, according to the statement by the UN children's fund Unicef and the refugee agency UNHCR.

More than one million children have meanwhile been internally displaced.

"No refugee crisis today worries me more than South Sudan," Valentin Tapsoba, Africa director for UNHCR said in Johannesburg today.

"That refugee children are becoming the defining face of this emergency is incredibly troubling."

South Sudan was plunged into a civil conflict when a split between President Salva Kiir and his former deputy Riek Machar escalated in December 2013.

Tens of thousands have been killed and 3.5 million displaced. About 100,000 people are facing a famine and one million are on the brink of famine.

- dpa