NAIROBI, Kenya - A decision by Islamic extremists to ban delivery of food aid and a "normalization of crisis" that numbed international donors to disaster made south-central Somalia the most dangerous place in the world to be a child.

The first in-depth study of famine deaths in Somalia in 2011 was released Thursday, and it estimates that 133,000 children under 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. That compares with 65,000 under-5 deaths in all industrial countries in the world combined during the same period, a population of 990 million, said Chris Hillbruner, a senior food security adviser at FEWS NET, a U.S.-sponsored famine warning agency.

"The scale of the child mortality is really off the charts," Hillbruner said from Washington.

FEWS NET was one of two food security agencies that sponsored the study. The other was the Food Security and Nutrition Analysis Unit-Somalia. The two agencies had warned the world as early as fall 2010 that failed rains in Somalia meant a hunger crisis was approaching.

"The world was too slow to respond to stark warnings . . . and people paid with their lives," said Senait Gebregziabher, the Somalia director for the aid group Oxfam. "These deaths could and should have been prevented."

The new study put the total number of famine deaths at nearly 260,000.

In March 2011, some 13,000 people died from famine, the study found. In May and June 30,000 people died each month - at least half of them children. The United Nations' formal declaration of famine did not happen until July.

Why was there such a slow humanitarian response?

One reason Hillbruner indicated was the feeling that Somalis are always suffering, what he called a "normalization of crisis."

In Washington, State Department spokesman Patrick Ventrell said the hardest-hit famine regions were controlled by the extremist Islamist group al-Shabab.

"Al-Shabab's inhumane blockage of humanitarian assistance prior to and during the famine, including banning dozens of humanitarian organizations from providing lifesaving assistance, thwarted a more rapid international rapid humanitarian response that could have saved even more lives," Ventrell said.