The African Union's mission in Somalia said it will withdraw 1,000 troops fighting militants in the country this year, as part of plans to pull out all soldiers by December 2020.

In a statement released Tuesday, the AU's special representative for Somalia Francisco Madeira called for urgent support to enable the national army to take over responsibility for the country's security."Troop movements have started in different parts of the country and will continue for the coming weeks," Madeira said.

"This is a process of realignment to effect the reduction in numbers and also begin the handover process of national security responsibility to the Somali National Security Forces."

African Union Mission in Somalia (AMISOM) troops deployed to Somalia in 2007 to defend the internationally-backed government against attacks by al-Shabaab terrorist group, an al-Qaida affiliate still carrying out attacks on civilian, military and government targets in the capital Mogadishu and elsewhere.

In 2016 the African Union announced an exit strategy which would see some 22,000 troops withdraw and hand over control of security to the national army.

Currently the bloated and largely ineffective Somali army is more a collection of clan militias, with various international militaries providing poorly-coordinated training to different units.

Al-Shabaab lost its foothold in Mogadishu in 2011, but has continued its fight, and was blamed for the country's worst ever attack in which a truck bombing left 358 dead in the capital last month.