US-led coalition troops battling suspected militants in southern Afghanistan lobbed a grenade that destroyed a house and killed 15 gunmen as well as a civilian woman and two children, the coalition said Monday. The troops were raiding compounds suspected of housing bomb makers in the Garmser district of Helmand province on Sunday when operatives attacked them with heavy fire, the statement said. Coalition forces responded with small-arms fire, killing several militants, it said. "During one of the engagements, several militants barricaded themselves in a building on the compound and engaged coalition forces with a high volume of gunfire. Coalition forces used a single grenade which killed the attacking militants," the statement said. "However, the building the militants were fighting from collapsed." After the clash, troops recovered the bodies of a woman and two children from the collapsed building, along with several militants and their weapons, it said. Another woman was wounded during the battle and was taken to a medical facility for treatment. Two suspected militants were detained for questioning, the coalition said. "We would like to express our heartfelt condolences to the families and loved ones of the deceased," said Maj. Chris Belcher, a coalition spokesman. "When militants knowingly engage coalition forces with innocent people in the background, it only shows the extremists' complete disregard for innocent lives," Belcher said in a statement. Civilian casualties have incited resentment and demonstrations against US and NATO forces in the past, though officials blame militants for using civilian homes as cover during clashes. President Hamid Karzai has pleaded with Western forces to do all they can to prevent such deaths. Also Monday, New Zealand Defense Minister Phil Goff announced that his nephew was killed in Afghanistan while fighting as a soldier for the US Army. Lieut. Matthew Ferrara, 24, held joint New Zealand-US citizenship and is the first New Zealander killed in the Afghan conflict. He was among six US Army troops and three Afghan soldiers killed in an ambush by insurgents in eastern Afghanistan on Saturday, Goff said in a statement. He said the soldiers had been with the NATO-led International Security Assistance Force. More than 5,800 people, mostly militants, have died in insurgency-related violence this year, a record, according to an Associated Press count based on figures from Western and Afghan officials.