Local officials in eastern Afghanistan say a NATO helicopter killed four Afghan police officers and wounded at least two civilians during an attack on militants late Wednesday.
Authorities in Ghazni province say the incident occurred in Deyak district. NATO officials say they are investigating the claims.
Last week, an air strike by a NATO helicopter supporting Afghan security forces killed nine suspected Taliban militants, as well as two civilians, in another area of Ghazni province.
Civilians casualties have long been a source of contention between Afghan President Hamid Karzai and the international coalition fighting in Afghanistan and has prompted NATO in the past to alter its strategies in order to further limit collateral damage.
However, international reports studying casualty rates throughout the 11-year Afghan war blame insurgents for a vast majority of civilian deaths.