The U.S. military in Afghanistan says coalition forces killed four Afghan policemen and wounded a fifth after mistaking them for militants.

The military says the incident occurred during a firefight Thursday, near Gereshk in Helmand province, when U.S. troops battling militants opened fire on an approaching vehicle carrying five armed men - all Afghan police officers out of uniform.

Afghan officials confirmed the Americans' account of the shooting. The U.S. military said the regrettable incident is being investigated.

Some information for this report provided by AP and Reuters.