LAGOS, Nigeria (AP) — Doctors Without Borders says it has given food to 26,000 families taking refuge from Boko Haram Islamic extremists in northeast Nigeria's biggest city, stepping outside its traditional medical role to try to prevent more children dying.

A statement Saturday says people are "in desperate need" and other organizations are not stepping up.

U.N. agencies and private charities operate in Maiduguri city alongside government agencies being investigated for corruption in food distribution. Refugees have almost doubled the population of Maiduguri, the birthplace of Boko Haram, to 2.5 million.

The United Nations last month appealed for $1 billion to tackle Africa's worst humanitarian crisis in which 5.1 million refugees face starvation in northeast Nigeria.

It warns many more could die in famine than the 20,000-plus killed in the seven-year Islamic uprising.