"They are trying to make it very impossible for the humanitarian groups," Lt. Colonel Paddy Ankunda of the African Union force told ABC.
The militant Islamic group has also refused to set up refugee camps in the southern territory it controls, forcing millions of starving people to walk for hundreds of miles.
The United Nations has officially declared a famine in southern Somalia.
One mother said she walked for 15 days with her children to reach the camp.
Her son, Yusef, said he doesn't miss home. "It was bad."