A decision by extremist Islamic militants to ban delivery of food aid and a ‘‘normalization of crisis’’ that numbed international donors to unfolding disaster made south-central Somalia the most dangerous place in the world to be a child in 2011.

The first in-depth study of famine deaths in Somalia in 2011 was released Thursday, and it estimates that 133,000 children younger than age 5 died, with child death rates approaching 20 percent in some communities.

That’s 133,000 under-5 child deaths out of an estimated 6.5 million people in south-central Somalia.