Kabul, Afghanistan (CNN) -- The commander of U.S. and NATO-led forces in Afghanistan apologized Wednesday after an investigation concluded that coalition troops accidentally killed nine civilians -- including some children -- in a strike Tuesday.
Gen. David Petraeus, commander of the NATO-led International Security Assistance Force (ISAF), said he would personally apologize to Afghan President Hamid Karzai after Karzai returns from a trip to London this week.
"We are deeply sorry for this tragedy and apologize to the members of the Afghan government, the people of Afghanistan, and, most importantly, the surviving family members of those killed by our actions," Petraeus said in a statement Wednesday.
Some children were among the dead, an ISAF spokesman said.
Preliminary findings of an investigation show that ISAF forces accidentally killed nine civilians in the Darah-Ye Pech district of Afghanistan's eastern Kunar province Tuesday, the statement said. The incident happened after insurgents fired rockets at a base used by U.S. and allied troops.
"These deaths should never have happened..." Petraeus said.
"Regrettably, there appears to have been an error in the hand-off between identifying the location of the insurgents and the attack helicopters that carried out the subsequent operations."
In a statement Wednesday, Karzai condemned the incident "in the strongest terms possible." He noted the incident occurred less than 10 days after another incident "that left many civilians dead in the same province."
On February 20, Kunar provincial Governor Sayed Fazlullah Wahidi said 64 civilians had died in a joint operation by ISAF and Afghan security forces over several days. The dead included 20 women and 15 children, he said. Karzai said the children were collecting firewood when they were killed.
Karzai emphasized Wednesday that "NATO needs to focus on the safe havens of terrorists," adding that killing innocent civilians will create "huge problems."
Civilian casualties have been a hot-button issue in Afghanistan and have hurt the coalition's efforts to win backing for its efforts. Petraeus recently directed military commanders in Afghanistan to review changes meant to minimize civilian casualties. He has ordered commanders to brief helicopter attack crews again on the changes, he said.
Should the facts of the investigation warrant it, he said, the military could take disciplinary action against some of the troops involved.
CNN's Matiullah Mati and Barbara Starr contributed to this report.