Nato has admitted that its forces were responsible for the deaths of three women during a botched night-time raid in eastern Afghanistan in February.
It had already admitted killing two innocent men in the operation, saying they were shot dead when they came out of their homes carrying firearms.
Nato now says the women were killed by shots fired at the men.
Nato officials had previously suggested the women were killed by unknown assailants hours before the raid.
There was no immediate comment from the Afghan government. Civilian deaths at the hands of foreign forces have been a source of increasing friction between it and Nato.
Some reports have suggested Nato soldiers tried to cover up the deaths of the women by removing bullets from the bodies.
'Protecting their families'
Nato initially denied involvement in the deaths of the women in the raid in the Gardez district of Paktia on 12 February, but now admits to having bungled the operation.
"While investigators could not conclusively determine how or when the women died, due to lack of forensic evidence, they concluded that the women were accidentally killed as a result of the joint force firing at the men," a Nato statement said.
The statement said Nato officials would apologise and pay compensation to the family of those killed.
"We deeply regret the outcome of this operation," said a Nato spokesman.
"The force went to the compound based on reliable information in search of a Taliban insurgent and believed that the two men posed a threat to their personal safety. We now understand that the men killed were only trying to protect their families."
One relative - whose two brothers, wife and sister were killed in the raid - said the family wanted the informant tried and put to death.
"Our demand is that this spy be executed in front of the people to ensure that such bad things don't happen again," he told the Associated Press news agency.
Karzai 'wants changes'
On Sunday, Afghan President Hamid Karzai called for an end to house searches by foreign troops.
Gen McChrystal (left) introduced new rules of engagement for Nato
He was visiting the southern city of Kandahar with top US commander Gen Stanley McChrystal to win support for an anti-Taliban offensive there.
"When there's an incident, he [McChrystal] comes and apologises," Mr Karzai told tribal leaders in the city, the birthplace of the Taliban.
"There've been changes in behaviour with the arrival of this new general, but we are still not convinced. I want more changes," Mr Karzai added.
Nato admits that its killing of civilians has undermined support for its mission in Afghanistan. But it points out that far more people are killed in attacks by the Taliban and other militants.
United Nations figures show the number of civilians killed by foreign and Afghan forces fell by 25% in 2009 compared with 2008. The UN says the vast majority of the 2,412 civilian deaths in 2009 were caused by militant attacks.
Gen McChrystal has introduced changes to Nato tactics aimed at cutting the risks to civilians. Measures include reducing the number of air strikes and night raids.