Barre did not give a reason for the reshuffle, which was read out by the Government Spokesperson in a video posted on the government's Facebook account.
Ahmed Moallim Fiqi Ahmed, who previously served as Foreign Minister and National Security Chief, was appointed Defence Minister, replacing Jibril Abdirashid.
Barre also appointed a new second Deputy Prime Minister, Jibril Abdirashid Haji Abdi, and a new Foreign Minister, Abdisaalan Abdi Ali Daay.
The appointment of a new Defence Minister comes as the government struggles to halt recent gains by al Shabaab in an offensive by the al Qaeda-allied group.
Al Shabaab briefly captured villages within 50 kilometres of Mogadishu, raising fears that the city could be targeted.
Somali forces have since recaptured those villages but al Shabaab has continued to advance in the countryside, as the future of international security support to Somalia appears increasingly precarious.
The group has been waging an insurgency since 2007, aiming to topple the government and establish its own rule based on a strict interpretation of sharia law.
--Reuters--