The attack took place in the central Somali town of Matabaan, in a region under the control of the Ahlu Sunna militia group, which supports the Somali government.
"It was a shocking attack. A gunman opened fire and killed a local NGO (aid group) worker and two World Food Programme staff members during distribution day," Abdi Ali Moalim, an aid worker in Matabaan, told Reuters.
The WFP said two staff members and one man working for a coordinating partner had been shot dead.
"The individual then gave himself up and is currently in the custody of the local authorities. WFP operations have been temporarily suspended in Matabaan," the relief agency said from Nairobi.
A spokesman for the Ahlu Sunna group said the gunman was in the group`s custody.
"We are investigating him," Sheikh Abdulaahi Abu Yusuf told Reuters. "We don`t know who was directly behind the case."
Last month the Islamist al Shabaab rebel group, which controls other parts of central and southern Somalia, announced a ban on 16 relief agencies in its territory.
Militants stormed and looted offices of aid organisations that are struggling to help tens of thousands of people at risk of starvation from the worst drought to hit the region in decades.
The Ahlu Sunna group controlling Matabaan and the surrounding area is against the hardline stances of the al Qaeda-linked al Shabaab. (*)
Editor: Kunto Wibisono
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