The U.N. children's agency says nearly 30 percent of young people between the ages of 15 and 24 in countries affected by conflict and disaster are illiterate, triple the global rate.

UNICEF said in a report released Wednesday that among these 59 million young people, girls are at the biggest disadvantage.

It says four impoverished African countries with a history of instability have the highest rates of young people unable to read or write — Niger with 76 percent, Chad with 69 percent, South Sudan with 68 percent and Central African Republic with 64 percent.

New UNICEF Executive Director Henrietta Fore says: "These numbers are a stark reminder of the tragic impact that crises have on children's education, their futures, and the stability and growth of their economies and societies."