A photograph the Afghan government distributed to back up its claims about civilian casualties in a US airstrike 10 days ago was actually a 2009 AFP photograph of a different funeral, a media investigation revealed Sunday.

The presidential palace gave journalists a dossier compiled by a fact-finding team sent by Afghan President Hamid Karzai to Parwan province to gather evidence on the airstrike on January 15.

Among the 14 photographs in the dossier is an AFP image taken on September 4, 2009 of a funeral in Kunduz province after a US airstrike that destroyed two fuel tankers, killing at least 70 civilians.

"We are taking this issue very seriously to find out who put this photograph in the dossier, which was made by several government departments," Aimal Faizi, spokesman for President Karzai, told AFP.

"There is no lack of evidence about the operation from at least ten other photos and matching video in the dossier, as well as from the families and survivors."

Faizi did not deny the photograph was misrepresented, but he accused The New York Times, which first investigated the error, of running a "politically motivated story to undermine general opinion about this incident".

"The truth is there -- that there were civilian casualties, houses were destroyed and that this was a unilateral operation and not in cooperation with local authorities," he said.

The New York Times on Sunday added that some of the material in the dossier was posted on a Taliban website two days before the government began handing it out.

It also raised questions over the authenticity of at least one other photograph in the dossier.

Karzai and the US-led NATO coalition both confirm there were civilian casualties in the joint Afghan-US operation on Taliban-held villages in Parwan province.

NATO said "several" civilians died during the 24-hour operation, without giving details, while Karzai backed the investigation team's conclusion that 12 civilians died.

Parwan governor Basir Salangi told AFP last week that six civilians had died and he accused the head of the investigation team, MP Abdul Satar Khawasi, of being a "treacherous liar" for exaggerating the death toll.

Civilian casualties have been one of the most sensitive issues of the 13-year military intervention in Afghanistan, and Karzai has often used misguided airstrikes to berate foreign countries and stir public anger.

He has focused on the Parwan deaths to castigate Washington as ties between the two allies fray badly over stalled negotiations on a deal to allow some US troops to remain in the country after 2014.

He has also angered western diplomats by drawing parallels between the Parwan casualties and a Taliban attack on a restaurant in Kabul on January 17 in which 21 people, including 13 foreigners, were killed.

At a government-organised press conference in Kabul on Sunday, families of the civilian victims of the Parwan operation denied that the photograph was from 2009 and insisted it was of a funeral after the attack 10 days ago.

Also on Sunday, a Taliban suicide bomber blew himself up near a military bus in Kabul killing two military officers and two civilians, while a roadside bomb in Helmand province killed six civilians.