Only Uganda and Burundi have sent peacekeepers to Somalia
Ugandan peacekeepers in Somalia have been selling arms to insurgents, a United Nations report says.
The report, by the UN monitoring group on the Somali arms embargo, says Ethiopia, Eritrea and Yemen are also breaking the embargo.
It cites one incident in which a group of Ugandan soldiers allegedly received $80,000 for a transaction.
Some peacekeepers are accused of setting up an arms trading network through translators.
The Ugandan army has already dismissed the accusations as "absolutely ridiculous."
The report says the soldiers received a wish-list of weapons from arms dealers and the weapons were then supplied from stores of equipment seized from insurgents.
Tens of thousands have fled the fighting in Mogadishu
The monitoring group says the weapons find their way back to the insurgent group they were captured from in the first place.
The report was presented to the UN Security Council by the head of the committee which has been monitoring the arms embargo, Dumisani Kumalo, who is South Africa's ambassador to the UN.
Mr Kumalo said there were grave concerns that some peacekeepers would do things to undermine the peace process.
The allegations have been sent to the Ugandan government, which has said it will carry out an inquiry.
The presence of Ethiopian troops in Somalia, backing the weak transitional government, also breaks the embargo, the report said.
The Ethiopians went into Somalia in 2006 to help oust Islamist forces which had taken control of Mogadishu.
Eritrea and Yemen are accused of backing the insurgents.
Somalia has been devastated by conflict since 1991 when former President Mohamed Siad Barre was ousted.