The UN Assistance Mission in Afghanistan (UNAMA) has voiced concern over the "rising" number of civilian casualties as a result of air strikes by the international coalition or the Afghan Air Force.
UNAMA said on September 25 it had received "multiple, credible allegations" that a strike hit the house of a teacher in the eastern province of Kapisa last week, killing nine members of the same family.
Those killed in the September 22 strike included three women and four children, a statement said. Six others were wounded.
Afghan Defense Ministry spokesman Mohammad Radmanish confirmed civilian casualties during a joint operation by Afghan and U.S. forces that involved air support.
He did not give details about the incident, but said an investigation was under way.
The U.S. Army in Kabul said it was reviewing information regarding the Kapisa incident, reiterating that it did all it could to avoid casualties among civilians.
"It isn't uncommon for insurgents to use these accusations to drive a wedge between the military and the population. We will provide updates as they become available," it also said in a statement e-mailed to Reuters news agency.
Afghan security forces have struggled to counter attacks from the Taliban and other militant groups since the withdrawal of most NATO combat troops in 2014.
In its statement, UNAMA urged all parties to the conflict to "uphold their obligations to protect civilians from harm."
It also reiterated its previous call for "government forces to uphold their commitment to regular review of targeting protocols and ensure mitigation measures and compensation for victims."
The number of civilians killed or wounded in air attacks has jumped by 52 percent in the first six months of this year, according to UN data.
The world body said 149 civilians were killed and 204 wounded in air strikes during the period, with women and children comprising more than half the casualties.