A Taliban suicide bomber rammed a car loaded with explosives into an armored NATO bus on a busy thoroughfare in Kabul Saturday, killing five NATO service members, including one Canadian soldier, eight civilian contractors and four Afghans.
It was earlier reported that the five soldiers and eight contractors killed were all American.
The British ministry said the families of the two civilians have been informed.
Prime Minister David Cameron offered condolences to families of the dead but insisted the attacks would not disrupt the work of international forces in Afghanistan.
The assault occurred just hours after top Afghan and Western officials met in the heart of Kabul to discuss the second phase of shifting security responsibilities to Afghan forces in all or part of 17 of the country's 34 provinces. Afghans already have the lead in the Afghan capital.
It was the deadliest single attack against the U.S.-led coalition across the country since the Taliban shot down a NATO helicopter on Aug. 6 in an eastern Afghan province, killing 30 U.S. troops, most elite Navy SEALs, and eight Afghans.
The Associated Press contributed to this report.