“I am deeply saddened by the reported killing and wounding of Afghan civilians,” Mr. Obama said in a statement. “This incident is tragic and shocking, and does not represent the exceptional character of our military and the respect that the United States has for the people of Afghanistan.”
An American soldier opened fire on villagers near his base in southern Afghanistan Sunday, killing 16, said Afghan President Hamid Karzai, who called it an “assassination” and furiously demanded an explanation from Washington. Nine children and three women were among the dead.
Defense Secretary Leon E. Panetta said the shooting suspect is in custody, adding that he had spoken with Mr. Karzai to assure him that “we will bring those responsible to justice.”
Gen. John Allen, the top U.S. commander in Afghanistan, spoke similarly Sunday, expressing his “deepest condolences” to the Afghan people and pledging that “anyone who is found to have committed wrongdoing is held fully accountable.”
U.S. officials said the service member was being detained in Kandahar and that the military was treating at least five wounded. One U.S. official said the soldier, an Army staff sergeant, was thought to have acted alone and that initial reports indicated he returned to the base after the shooting and surrendered.
One official, speaking on the condition of anonymity, said the shooter is a soldier from Joint Base Lewis-McChord in Washington state, assigned to support a special-operations unit of either Green Berets or Navy SEALs engaged in a village-stability operation.
The killing spree deepened a crisis between U.S. forces and their Afghan hosts over Americans burning Muslim holy books on a base in Afghanistan. The burnings sparked weeks of violent protests and attacks that left about 30 dead. Six U.S. service members have been killed by their Afghan colleagues since the Koran burnings came to light, but the violence had just started to subside.
“This is an assassination, an intentional killing of innocent civilians and cannot be forgiven,” Mr. Karzai said in a statement. He said he has demanded repeatedly that the U.S. stop killing Afghan civilians.
Mr. Obama called Mr. Karzai on Sunday “to express his shock and sadness at the reported killing and wounding of Afghan civilians,” the White House said. The White House press secretary’s office added that during the call, Mr. Obama “reaffirmed our deep respect for the Afghan people and the bonds between our two countries.”
Mr. Obama learned of the shootings Sunday morning from senior national security staff and received a briefing before calling Mr. Karzai, said deputy National Security Council spokeswoman Caitlin Hayden.
The violence over the Koran burnings spurred calls in the U.S. for a faster exit strategy from the 10-year-old Afghanistan war. Mr. Obama said recently that “now is the time for us to transition.” But he also said he had no plan to change the timetable that has Afghans taking control of security countrywide by the end of 2014.
Republican presidential hopeful Newt Gingrich, in an appearance on “Fox News Sunday,” said he thinks U.S. involvement in the region around Afghanistan may be risking the lives of young troops in a mission that “may not be doable.”
The tensions between the two countries appeared to be easing as recently as Friday, when the U.S. and Afghan governments signed a memorandum of understanding about the transfer of Afghan detainees to Afghan control — a key step toward an eventual strategic partnership to govern U.S. forces in the country.
But Sunday’s shooting could push that agreement further away.
“This is a fatal hammer blow on the U.S. military mission in Afghanistan. Whatever sliver of trust and credibility we might have had following the burnings of the Koran is now gone,” said David Cortright, director of policy studies at the University of Notre Dame’s Kroc Institute for International Peace Studies and an advocate for a quick withdrawal from Afghanistan.
“This may have been the act of a lone, deranged soldier, but the people of Afghanistan will see it for what it was — a wanton massacre of innocent civilians,” Mr. Cortright said.
One of the survivors, a 15-year-old boy named Rafiullah who was shot in the leg, spoke to Mr. Karzai by phone and described how the American soldier entered his house in the middle of the night, woke up his family and began shooting them, according to the Afghan president’s statement.
An Associated Press photographer saw 15 bodies between the two villages caught up in the shooting. Some of the bodies had been burned, while others were covered with blankets. A boy partially wrapped in a blanket was in the back of a minibus, dried blood crusted on his face and pooled in his ear. His loose-fitting brown pants were partly burned, revealing a leg charred by fire.
Villagers packed inside the minibus looked on with concern as a woman spoke to reporters. She pulled back a blanket to reveal the body of a smaller child wearing what appeared to be red pajamas. A third dead child lay amid a pile of green blankets in the bed of a truck.
• This article is based on wire service reports.