Updated at 3:31 p.m. ET
(CBS/AP) BALANDI, Afghanistan - Taliban insurgents opened fire on two brothers of Afghan President Hamid Karzai as they left a memorial service Tuesday for 16 villagers allegedly killed by a U.S. soldier.
Qayum and Shah Wali Karzai and other top Afghan officials in their delegation escaped in their cars unharmed from the ambush in the country's south.
CBS News correspondent Mandy Clark reports that one Afghan soldier was killed in the attack.
The soldier was protecting the two men as part of a high-level government delegation that was visiting one of the two villages where the killings took place. He was shot in the head almost instantly and died.
Two other Afghan army personnel were wounded in the 20-minute firefight that ensued in one of the two villages in Kandahar province where the killings had occurred two days before.
The gunbattle came as images of the aftermath of Sunday's killings spread across the country, and the public reaction which at first seemed surprisingly muted began to build.
In the east, students staged the first significant protest in response to the killings, raising concerns about a repeat of the wave of violent demonstrations that rocked the nation after last month's burning of Korans by troops at a U.S. base.
Burning an effigy of President Obama and chanting "Death to America," the protesters in the city of Jalalabad demanded the U.S. soldier face a public trial in their own country, Clark reports.
The incident has also added to pressure in the U.S. to get out of Afghanistan more quickly. Defense Secretary Leon Panetta, speaking to reporters on the plane traveling to Bishkek, Kyrgyzstan, said the military withdrawal was still on schedule to finish by 2014.
Panetta said he was awaiting plans from Gen. John Allen, the top commander in Afghanistan, to bring home the remaining 23,000 U.S. troops sent to Afghanistan during the 2009 surge. Those forces are due to leave by the end of September, dropping the U.S. presence in the country down to 68,000 troops.
On Tuesday, Mr. Obama .
"The United States takes this as seriously as if it was our own citizens and our own children who were murdered," Mr. Obama told reporters in Washington.
"I can assure the American people and the Afghan people that we will follow the facts wherever they lead us, and we will make sure that anybody who was involved is held fully accountable with the full force of the law," he said.
Taliban spokesman Qari Yousef Ahmadi claimed responsibility for the attack on the delegation in Balandi village in Panjwai district, an area considered the birthplace of the militant group. Previously, the movement had vowed to behead those responsible for the shootings.
The militants rode to the village on motorcycles, police said. They ambushed the delegation from the cover of a distant row of trees. Afghan security forces fired back, killing three militants, said Gen. Abdul Razaq, the Kandahar police chief. The two Afghan army personnel who were wounded included a soldier and a military prosecutor, he said.
Qayum Karzai sought to play down the ambush. He said the delegation, which also included Kandahar Gov. Tooryalai Wesa and Minister of Border and Tribal Affairs Asadullah Khalid, had been giving their condolences to the victims' families. They then heard "two very, very light shots."
"Then we assumed it was the national army that started to fire in the air," said Karzai.
Nine of the 16 civilians killed on Sunday in Balandi and Alkozai villages were children and three were women, according to the Afghan president. Some of their bodies were burnt after they were killed.
The U.S. has an Army staff sergeant in custody who is suspected of carrying out Sunday's pre-dawn killings but has not released his name.
Villagers have described the gunman stalking from house to house in the middle of the night, opening fire on sleeping families and then burning some of the dead bodies.
Witnesses interviewed by The Associated Press after the attack described only one shooter, and U.S. officials have been adamant that there was only one soldier involved.
On Tuesday, villagers who testified to the delegation insisted there were two soldiers, citing relatives who survived the attacks.
Mohammad Wazir, who was away from his home in Balandi village that night, said his sister saw two U.S. soldiers enter the house and start shooting. Everyone started running different directions, and she ran to the kitchen to hide. When the gunfire ended and she re-emerged, 11 of her relatives were dead.
In Alkozai to the south, a man named Sayed Jan said his cousins told him that they saw two soldiers come into his house and start firing. Jan's relatives barricaded their door and snuck out another exit. Jan was away in Kandahar city that night.
The villages are about 40 miles southwest of Kandahar city.