Insurgents have killed eight CIA agents at a military base in Afghanistan, and four Canadian soldiers and a journalist on patrol.
US officials say the Americans, who were killed in a suicide bombing at a military base in southeastern Khost province, were CIA agents, Reuters reports.
Taliban spokesperson Zabihullah Mujahid says the attack was carried out by a valorous Afghan army member when the agents were busy gaining information about the mujahideen.
He made the statement in an email reply to Reuters' questions.
Earlier reports said eight US civilians had been killed at Forward Operating Base Chapman in eastern Afghanistan, and no US or NATO troops were injured.
CIA officials were not immediately available to comment, and the US authorities say they cannot provide details until the agents' families have been notified.
The explosion caused one of the highest foreign civilian death tolls in an insurgent strike in the eight-year war.
Canadian officials say the Canadians, who included a journalist from the Calgary Herald, were killed when their armoured vehicle was hit by a bomb in southern Kandahar province.
US denies killing civilians
Meanwhile, the US military has denied killing several teenage schoolchildren during a raid in eastern Afghanistan, the ABC reports.
The Afghan government has accused American troops of killing 10 civilians, including eight teenagers, in an attack on what has been described as a family fort in the eastern city of Jalalabad.
The incident has sparked anger in Afghanistan and anti-US rallies have been held in several cities, with people shouting "death to Obama" and calling for an inquiry into the deaths.
NATO initially denied the attack, but now says US Special Forces conducted a raid in the isolated area on Saturday.
But the US says the victims were all men of fighting age, who were shot dead after weapons and bomb components were found in a compound.
The Afghan government says it has evidence the victims were students who were attending a local school.