Washington: The eight American civilians killed in a suicide bombing at a military base in southeastern Afghanistan on Wednesday were all CIA agents, US officials said.
The explosion was at a military base in Khost province, near the border with Pakistan, US officials said.
The base is a centre for personnel working on reconstruction projects as part of US President Barack Obama`s strategy to try to stabilise the country after eight years of war.
"We can confirm that there was an explosion in Khost province and eight Americans have been killed," said a US official in Kabul.
Several others, none of them US or NATO troops, were wounded in the explosion at Forward Operating Base Chapman, defence officials said, without providing any further details.
CIA officials in Washington were not immediately available for comment and US officials said they could not provide details pending notification of the agents` families.
Separately, four Canadian soldiers and a Canadian journalist were killed when their armoured vehicle was hit by a bomb in southern Kandahar province, the Canadian Defence Ministry said.
Attacks in Afghanistan this year have spiralled to their highest levels since the Taliban were overthrown by US-backed Afghan forces in late 2001.
Civilian and military casualty tolls have reached record levels this year, with suicide attackers even targeting United Nations employees at a guesthouse in Kabul, killing five and wounding several others.
The agency has been expanding its presence in Afghanistan in a bid to stem Taliban gains.