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 .
NEW : Karzai condemns the attack . Helicopters attacked after insurgents fired rockets at government troops . Several civilians were killed , including some children . Gen. David Petraeus apologizes .