Five African Union peacekeepers in Somalia have been arrested over alleged illegal sales of military supplies, the African Union Mission in Somalia (AMISOM) said Monday.

AMISOM said the soldiers were found in possession of fuel and sand bags and were detained Sunday in a joint operation with Somali police that followed an investigation and a period of surveillance.

"AMISOM exercises zero tolerance to unprofessional conduct among its personnel and the culprits will be prosecuted in accordance with the law," read a statement from AMISOM, which has over 22,000 peacekeepers in Somalia.

"All personnel serving under the African Union Mission in Somalia are bound by the AMISOM Code of Conduct and any deviation from the standards set therein will be met with the full might of the law."

AMISOM promised "requisite steps to ensure that this practice is uprooted from within its ranks" to ensure such "selfish acts" did not derail its mission.

The Mission did not reveal the nationality of the soldiers but Ugandan defence minister Paddy Ankunda later told AFP that they came from Uganda.

"An investigation is underway. If they are found guilty, the law will follow its course," he said.

AMISOM's task is to shore up Somalia's internationally-backed but fragile government in the face of threats from Al Qaeda-affiliated Shabaab extremists.

Deployed in 2007, AMISOM drove the group from Mogadishu in 2011 but the extremists have continued their bid to overthrow the government, launching regular attacks on military, government and civilian targets in Mogadishu and elsewhere.

Recent months have seen a clutch of deadly Shabaab attacks on restaurants and hotels in the capital.

Last week at least 10 people killed after a car bomb attack and an assault by gunmen outside the Ambassador Hotel in the heart of Mogadishu.

AMISOM said two parliamentarians were among the dead and some 40 people were injured.