More than 1 million children have fled South Sudan's civil war, two United Nations agencies said Monday, part of the world's fastest growing refugee crisis. Another 1 million South Sudanese children are displaced within the country, having fled their homes due to the civil war, said the U.N.'s child and refugee agencies in a statement Monday.

"The future of a generation is truly on the brink," said Leila Pakkala, UNICEF's Regional Director for Eastern and Southern Africa. "No refugee crisis today worries me more than South Sudan," said Valentin Tapsoba, UNHCR's Africa Bureau Director. "That refugee children are becoming the defining face of this emergency is incredibly troubling."For children still living in South Sudan, the situation is still grim. Nearly three quarters of children are out of school, according to the U.N. statement, which is the highest out-of-school population in the world. An official famine was declared in two counties of South Sudan in February, and hundreds of thousands of children are at risk of starvation in the absence of food aid, according to the U.N. More than one thousand children have been killed or wounded in the East African nation's civil war. Both sides have pledged not to recruit child soldiers, but have ignored their promises.