Humanitarian aid supplies worth £480,000 - funded by UK taxpayers - were seized by al-Qaeda-linked militants in Somalia, it has emerged.
Supplies were in warehouses captured in a raid by al-Shabab in November 2011, the Department for International Development's (DfID) accounts reveal.
DfID would not specify what those supplies included. It said all material was destroyed in the raid or later.
A DfID spokesman said working in "fragile states carries inherent risk".
The department's annual accounts said the £480,000 was written off "following the theft between November 2011 and February 2012, by al-Shabab in southern Somalia, of DfID-funded humanitarian materials and supplies from the offices and warehouses of partner organisations, to which DfID had provided funding to deliver projects and programmes".
The accounts said DfID's partners had "no prior warning of the confiscations being carried out and therefore had no time to prevent the loss by relocating goods".
And they added: "DfID continues to work with its partner organisations to ensure that risks like this are identified and that the organisations take appropriate action.
"This can include putting effective controls in place, where possible, to mitigate and/or eliminate such risks which reduce the effectiveness of our aid."
A department spokesman said: "DfID works in some of the most dangerous places in the world, including Somalia, because tackling the root causes of poverty and instability there ensures a safer world and a safer UK.
"Working in conflict-affected and fragile states carries inherent risk."
He said DfID did all it could "to mitigate against this but, on occasion, losses will occur".
"We work with our partners to design programmes that protect our investment from misuse or theft."
Shadow international development secretary Ivan Lewis said the revelations suggested the "performance of our aid programmes has deteriorated" under the coalition.
"We support their decision to spend less than one penny in every pound of UK spending on helping to eliminate poverty in the world," he said.
"It is morally the right thing to do and in our national long-term national interest. But they have a duty to ensure taxpayers' money is being used appropriately and effectively."