Thousands of Afghans protested at the scene of the killings, blocking the main road between the Afghan capital, Kabul, and the Pakistan border and throwing rocks at police.
Many chanted: "Death to America! Death to Karzai!" in a reference to the Hamid Karzai, the Afghan president.
Pedestrians 'shot at'
More than a half dozen Afghans injured in the shooting told the Associated Press news agency that US soldiers had shot at pedestrians and passing cars indiscriminately along a five-kilometre stretch of one of eastern Afghanistan's busiest roads.
|The attacks provoked |
an angry reaction [Reuters]
"They were firing everywhere, and they even opened fire on 14 to 15 vehicles passing on the highway," said Tur Gul, 38, who was shot twice in the hand as he stood by the roadside.
"They opened fire on everybody, the ones inside the vehicles and the ones on foot."
One man told Al Jazeera five members of his family were killed in the shooting
"American bullets murdered my family ... it's tyranny and injustice, he said."
Mohammad Khan Katawazi, the district chief of Shinwar, said the Americans had treated every person and car along the road as a potential attacker.
Abdul Nangahar, the province's police chief, said: "When local people came to the scene, the soldiers just opened fire on the crowd. People got killed and wounded."
Al Jazeera correspondent John Cookson said that sucide car bombs are increasingly common in Afghanistan.
He said: "The message is people are fed up with foreign troops on their soil."
It was also reported that the US military deleted any pictures and footage of the scene, Cookson said.
Soldiers 'firing around'
Several victims at a hospital in Jalalabad said American troops travelling in a convoy on the road opened fire on them without.
As the convoy neared, many cars pulled over to the side of the road, but the soldiers still opened fire on them, they said.
"When we parked our vehicle, when they passed us, they opened fire on our vehicle," said 15-year-old Mohammad Ishaq, who was hit by bullets in his left arm and his right ear.
"It was a convoy of three American Humvees. All three Humvees were firing around," he said.
Ahmed Najib, 23, who was hit by a bullet in his right shoulder said: "One American was in the first vehicle, shouting to stop on the side of the road, and we stopped.
"The first vehicle did not fire on us, but the second opened fire on our car,"
Najib said his two-year-old brother was grazed on his cheek by a bullet.
"I saw them turning and firing in one direction, then turning and firing in another. I even saw a farmer shot by the Americans," he said.
The US military said in a statement its troops fired in self-defence as they fled after the car bomb attack.
Major William Mitchell, a US military spokesman, said: "We certainly believe it's possible that the incoming fire from the ambush was wholly or partly responsible for the civilian casualties," he said.
Wakil Ahmed Mootawakeel, the Taliban's former foreign minister and senior aide to Mullah Omar, the Taliban's leader, told Al Jazeera: "They [foreign troops] must go immediately. Things must change in Afghanistan. We want peace, not war."
Cookson said: "The bombers are hoping to destabilise Afghanistan further and cause fear and unease among the general population.
"Meanwhile, the Taliban are consolidating control of the south and promising security."
Nato's International Security Assistance Force also announced on Sunday that two soldiers had died in fighting in southern Afghanistan on Saturday. It did not give their nationalities.