KABUL (Reuters) - The U.S. military is investigating an air strike near the northern city of Kunduz last week following reports that as many as 14 civilians, including women and children, were killed in the attack, a statement said on Wednesday.

Last week, Afghan officials confirmed the deaths, which occurred during an operation on July 19 by Afghan security forces backed by U.S. air strikes, but said the causes were unclear.

A separate U.S. statement last week confirmed that U.S. aircraft had carried out strikes in support of the operation but said there were no indications they had caused any civilian casualties.

On Wednesday, the U.S. military issued a second statement saying that the incident was being investigated.

“While an on-the-ground assessment conducted by Afghan forces immediately following the strikes revealed no indications the strikes caused civilian casualties, we are investigating the incident and subsequent claims further,” said U.S. Army Lt. Col. Martin O’Donnell, spokesman for U.S. Forces-Afghanistan.

“U.S. Forces-Afghanistan takes all allegations of civilian casualties seriously and is working closely with the Afghan government and Afghan National Defense and Security Forces to determine the facts surrounding this incident,” the statement said.

STRATEGIC

Kunduz, a key strategic target for the Taliban in northern Afghanistan, has seen repeated instances of civilians killed in air strikes by both U.S. and Afghan air forces, most notably in 2015 when a hospital operated by aid group Medecins Sans Frontieres was hit, killing 42 people.

In April, local people in Dasht-i Archi district in Kunduz province said dozens were killed when an Afghan strike hit a religious ceremony.

As the United States has stepped up its air operations in Afghanistan and the Afghan air force has begun conducting more operations of its own, the number of civilian casualties from air strikes has risen sharply.

In the first six months of the year, the United Nations reported a 52 percent jump in civilian casualties from air strikes, with 149 people killed and 204 injured. Overall civilian casualties remained roughly stable.

In a separate statement on Wednesday, the U.S. military said an air strike in support of an Afghan special forces operation had killed Mullah Nasim Mushfaq the shadow governor of Kapisa province, north of Kabul as well as Qari Ehsanullah, shadow governor of Tagab district in the province.