A NATO air strike killed four Afghan police and two civilians on Thursday, Afghan officials said.
A spokesman for the US-led NATO force in Kabul said that the military was checking the information.
The attack happened after Taliban insurgents attacked a local police post in eastern Ghazni province before dawn and NATO planes were called in to support the officers under attack.
"The NATO planes went there to assist the police, but the post was bombed and four police were killed. Two civilians present were also killed," Fazul Ahmad Tolwak, chief of Ghazni's Deh Yak district said.
Ghazni provincial administration spokesman Fazul Sabawoon confirmed the incident and gave a similar account.
In February, Karzai said he would issue a decree ordering an end to local security forces calling in NATO air strikes amid new tensions over civilian casualties caused by such attacks.
Air strikes have been an important weapon in the fight against Taliban insurgents, but they have also proved hugely controversial as they have led to numerous civilian deaths.
U.S. General Joseph Dunford, who took charge of the U.S.-led NATO force in the war-battered country in February, said he was prepared to comply with Karzai’s order, after an airstrike in the same month killed 10 people mostly women and children.
However it is unclear whether the ban has been enforced and many operations are jointly run by NATO and Afghan forces.
Last week Afghan officials said four civilians, including a child, were killed in a two-day raid against Taliban insurgents by Afghan and international forces in the province of Logar, south of the capital Kabul.
NATO's International Security Assistance Force said it was also investigating those accusations.