By ADAM B. ELLICK and ABDUL WAHEED WAFA, The New York Times
KABUL, Afghanistan — A day after a fierce suicide bombing in southern Afghanistan, insurgents struck an American military convoy in a crowded market in the eastern part of the country Thursday, and officials said one soldier and 18 civilians were killed.

One of the victims was a 12-year-old boy, who died when a suicide car bomber in a Toyota Corolla approached the convoy and then swerved into a weekly market around 8 a.m., according to American and Afghan accounts. Dr. Ajmal Pardes, the director of public health in the area, said 74 people were wounded.

The strike was in the Bati Kot district of eastern Afghanistan’s Nangarhar Province.

An Associated Press photographer said that an American military vehicle, two civilian vehicles and two rickshaws were destroyed.

Cmdr. Jeff Bender of the Navy, an American military spokesman in Kabul, said the civilian death count, initially put at 10, had risen to 18.

On Wednesday, a tanker truck packed with explosives detonated outside the provincial council office in Kandahar, Afghanistan’s largest southern city, killing the driver and at least six other people and wounding more than 40 others.

The blast shook the entire city, caused at least five houses to fall and left a crater near the council building, which housed an office of a national security service.

“The enemies of Afghanistan and peace once again put us in mourning,” Gen. Rahmatullah Roufi, the provincial governor, told reporters. He announced a “purification” operation to arrest insurgents in and near the city.

In a separate incident reported on Thursday, two soldiers from the American-led NATO alliance were killed in an explosion in the south of the country in an explosion on Wednesday, the alliance said, but did not specify the soldiers’ nationality.

The Defense Ministry in London later identified the two soldiers as members of Britain’s Royal Marines who were taking part in a joint patrol with Afghan soldiers in the Garmsir district of Southern Helmand Province.

The American contingent is the largest foreign force in Afghanistan, but Britain has about 8,000 troops there. A survey broadcast Thursday by the BBC said more than two-thirds of those questioned believed that Britain should withdraw its soldiers over the next year while less than a quarter favored their continued deployment.

This year has been the bloodiest since the American-led invasion of late 2001 that toppled the Taliban regime, whose supporters have revived their campaign to drive out foreign forces.

The latest American fatalities brought to around 148 the number of American military deaths so far this year, compared to 111 in the whole of 2001, The A.P. reported. Additionally, around 110 soldiers from other coalition forces have died this year.

More than 5,400 people, including almost 1,000 civilians, have died in violence related to the insurgency this year, the news agency said, citing figures provided by Afghan and international officials.