The coalition commander in Afghanistan went to the site of a recent airstrike and apologized for civilian deaths, NATO's International Security Assistance Force said Friday.

ISAF Commander Gen. John Allen paid his condolences to survivors of victims in Logar province, southeast of the capital, Kabul.

Sahib Khan, a member of the Afghan parliament from Logar, said Wednesday's airstrike killed 18 people, including women and children, near the volatile Pakistan border.

NATO forces said the strike occurred when soldiers returned fire during a mission targeting a Taliban leader. An ISAF spokesman said insurgents were killed and security forces seized weapons and explosives.

The allegations of civilian casualties reverberated through the Afghan government and Washington as U.S. Defense Secretary Leon Panetta arrived in Kabul for talks on Thursday.

Afghan President Hamid Karzai condemned the strike, saying, "NATO operations that inflict human and material losses to civilians can in no way be justifiable, acceptable and tolerable."

Panetta did not address the controversy over the airstrike in his public remarks while in Kabul. The news came ahead of discussions between Panetta, Allen and Afghan Defense Minister Gen. Abdul Rahim Wardak.

While militant attacks have caused by far the greatest number of civilian casualties in Afghanistan, many Afghans and coalition members have expressed concern about civilian deaths caused by air operations.

The latest allegations of civilian casualties also come at a critical time for the United States. Though U.S. military and political officials have said publicly that Afghanistan will be ready to take over security of its country by the time NATO troops depart, critics have said there are questions about whether Afghan forces can stand on their own.