Eight CIA agents have been killed in Afghanistan as insurgents intensify their campaign.
Wearing an explosive vest, a bomber managed to enter Forward Operating Base Chapman in Khost Province, on the border with Pakistan.
The Khost base is engaged in reconstruction projects, a key part of President Obama’s strategy to stabilise the country.
In a separate attack, four Canadian soldiers and a journalist died when their armoured vehicle was blown up in the southern province of Kandahar.
The Canadian team was also working on community reconstruction projects.
Foreign aid agencies argue that using military personnel to carry out development projects risks blurring the lines between troops and civilians.