Kabul, Afghanistan (CNN) -- Ten parliamentary campaign workers were killed in a NATO airstrike in northeastern Afghanistan on Thursday, a provincial official said.
The incident -- which took place ahead of the September 18 parliamentary election -- occurred in the Rostaq district of Takhar province, where NATO says it was targeting a militant.
Afghan President Hamid Karzai, who has consistently deplored civilian casualties in the war, condemned the strike, which occurred on the same day he's scheduled to meet with U.S. Defense Secretary Robert Gates.
Faiz Mohammad, spokesman for the provincial governor, said the event happened because NATO-led and Afghan security forces are not coordinating their activities properly.
NATO's International Security Assistance Force told CNN it is "still looking into this situation" and "gathering the facts."
"We're aware of the allegations that this strike caused civilian causalities and we'll do our best to get to the bottom of the accusations," U.S. Marine Corps Maj. Gen. David Garza, an ISAF official, said in a press release.
"What I can say is these vehicles were nowhere near a populated area and we're confident this strike hit only the targeted vehicle after days of tracking the occupants' activity."
Along with the deaths, candidate Abdul Wahid Khorazani and another campaign worker were injured, Mohammad said. He said the civilians were campaigning for Khorazani at the time.
ISAF said it carried out "a precision airstrike targeting an Islamic Movement of Uzbekistan senior member," determined to be the deputy shadow governor for Takhar.
"Intelligence tracked the insurgents traveling in a sedan on a series of remote roads in Rustaq district. After careful planning to ensure no civilians were present, coalition aircraft conducted a precision airstrike on one sedan and later followed with direct fire from an aerial platform. The vehicle was traveling as part of a six-car convoy, but no other vehicles were hit in the strike," the military said.
ISAF wasn't able to get a ground force to the region right away, but "initial reflections indicate eight to 12 insurgents were killed or injured in the strike, including a Taliban commander."
CNN's Joe Sterling contributed to this report