KABUL, Afghanistan -- A suicide bombing aimed at a US military convoy triggered a chaotic round of gunfire on a busy highway in eastern Afghanistan yesterday, leaving at least eight Afghan civilians dead and about three dozen others wounded, officials said.

KABUL, Afghanistan -- A suicide bombing aimed at a US military convoy triggered a chaotic round of gunfire on a busy highway in eastern Afghanistan yesterday, leaving at least eight Afghan civilians dead and about three dozen others wounded, officials said.

The attack and resulting gunfire, which occurred outside the city of Jalalabad, set off a stone-throwing riot in which hundreds of protesters, alleging that US troops fired indiscriminately on civilians, shouted slogans denouncing the United States and the government of President Hamid Karzai.

It was the highest civilian death toll this year in a matter involving US or other foreign troops. Such casualties erode public support for Karzai's government, and the Afghan president has made repeated public appeals to allied forces to exercise greater care to avoid killing or wounding civilians.

The shooting occurred as a five-vehicle US convoy patrolled near the Jalalabad airfield, a large base just off a heavily traveled highway between the Pakistan border and Kabul, the Afghan capital.

US military officials said American forces opened fire after a suicide attacker detonated a minivan packed with explosives as the convoy passed through the small market town of Bari Kot, whose bazaar was filled with morning shoppers.

Calling the ambush "complex," the military said that, simultaneously with the suicide attack, US troops came under small-arms fire from several directions.

Witnesses, however, said gunfire following the explosion appeared to come mainly from US troops whose convoy sped along the highway shooting in the direction of other vehicles and pedestrians for up to 5 miles from the blast scene.

"They were firing everywhere," Tur Gul, a witness, said. Gul, who was standing at the roadside and suffered gunshot wounds, said he saw more than a dozen cars hit.

"They opened fire on everybody, the ones inside the vehicles and the ones on foot," he said.

Allied military officials blamed the Taliban for the civilian casualties, saying the attackers bore responsibility whether bystanders were hit by fire from US troops or insurgents.

"We regret the death of innocent Afghan citizens as a result of the Taliban extremists' cowardly act," said Lieutenant Colonel David Accetta, a spokesman. "Once again the terrorists demonstrated their blatant disregard for human life by attacking coalition forces in a populated area, knowing full well that innocent Afghans would be killed and wounded in the attack."

Casualty counts varied, as is often the case in such attacks. Provincial police spokesman Abdul Ghafor said 10 people were killed and about three dozen injured.

The US military initially reported 34 civilians killed and 24 wounded, but later revised its death toll downward to eight, with 35 hurt.

A US serviceman also was wounded. The civilian dead were said to include two children.

Following the attack, angry demonstrators blocked the roadway near Jalalabad and hurled rocks at police. "Death to America! Death to Karzai!" some shouted.

Afghan and US military officials announced they would investigate the shootings, which came as the country braced for an expected new round of fighting, with warming temperatures that will soon melt the snow in mountain passes. Both NATO generals and Taliban commanders have declared their forces will seek to seize the offensive