Five soldiers with the African Union mission in Somalia (Amisom) and 10 Somalis have been arrested for selling military equipment, police say.
They were found with improvised detonators, fuel, sandbags and empty ammunition boxes.
Amisom confirmed the arrests saying it would not accept “unprofessional conduct among its personnel”.
The mission is fighting alongside Somali government forces against al-Shabab Islamist militants.
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This is the first time African Union troops have been arrested in Somalia since Amisom was established nine years ago, our correspondent says.
The authorities say the five AU soldiers are from Uganda, which has the largest number of troops in the 22,000-strong mission.
The police said they caught the men as they were trying to sell the equipment to civilians.
Somalia’s police chief Mohamed Sheikh Hassan Hamud told reporters that the Amisom troops had been under surveillance for a while after allegations that they were involved in the illegal trade.
”The Somali police have been investigating repeated claims that equipment and other resources meant for the Amisom forces were ending up in the hands of people who were misusing them,” he said.
Somalia’s Interior Minister Abdirizak Omar Mohamed said the sale of equipment may “explain why insecurity is increasing in Somalia”.
The 15 men are expected to appear in court in Mogadishu soon.