The International Security Assistance Force (ISAF) said in a statement that it was sending a team to Afghanistan's Laghman Province to investigate civilian casualties as a result of a NATO air strike.
NATO confirmed an air strike on September 16 "on a large group of armed individuals showing hostile intent," according to the ISAF statement.
ISAF said the air strike killed several insurgents but also caused "the unintentional deaths of a number of Afghan civilians."
Local Afghan officials said eight women gathering wood were killed in the NATO attack, near the village of Alingar.
The ISAF statement said coalition forces took civilian casualties "seriously" and promised a complete assessment of the incident.
ISAF offered its "sincerest regret to the families" of civilian victims of the strike.
Meanwhile, Afghanistan's government has denounced the deadly air strike.
A statement issued after a cabinet meeting headed by President Hamid Karzai on September 17 said the attack was "unjustifiable" and violated a memorandum of understanding between Kabul and Washington.