Afghan President Hamid Karzai has "strongly condemned" the killing of a woman and her two children in what he described as a U.S. air strike in the east of the country.
The bombing reportedly took place in Khost Province on the night of April 14.
The U.S.-led military coalition in Afghanistan said it is looking into the incident, adding that "ISAF takes all allegations of civilian casualties seriously."
Karzai called the strike a violation of agreements between the two countries.
Civilian casualties have long been a source of friction between the Afghan government and U.S.-led NATO troops, who are preparing to withdraw by the end the year.
Such incidents are one of the main reasons Karzai has cited for refusing to sign an agreement that would allow U.S. forces to stay beyond 2014.
Based on reporting by dpa, AFP, and Reuters