KABUL, Afghanistan — The Taliban struck here at the heart of the Afghan capital Tuesday, with a suicide bomber steering his explosives-laden Toyota minibus into an American convoy as it moved through the thick of rush-hour traffic. The attack killed 18 people, including 5 American soldiers and an officer from Canada, and wounded at least 47 civilians.
The assault, which brought mayhem and carnage to one of the capital’s main thoroughfares, comes as Afghan leaders and NATO commanders are preparing to launch a major offensive in the southern city of Kandahar, the Taliban’s spiritual home. If nothing else, the attack seemed intended to remind American and Afghan leaders of what the next several months might hold in store as the offensive unfolds.
Less than 24 hours later, Taliban insurgents attacked the American base at Bagram, 50 miles north of Kabul, setting off a gun battle early Wednesday morning that wounded at least five American soldiers.
The American command confirmed that an attack was unfolding, saying American troops had killed seven of the attackers.
The attack in the center of Kabul on Tuesday pushed the number of Americans killed in Afghanistan-related operations to more than 1,000 since the American and NATO-led campaign began here in the autumn of 2001. The blast sent a fireball billowing into the air, set cars aflame and blew bodies apart. Limbs and entrails flew hundreds of feet, littering yards and walls and streets. The survivors, many of them women and children, some of them missing limbs, lay in the road moaning and calling for help.
In a passenger bus, an Afghan woman lay dead in her seat, cut in half, with her baby still squirming in her arms. Fifty yards away, a man’s head lay on the hood of a truck.
“I just dove on the ground to try to save myself,” said Mahfouz Mahmoodi, an Afghan police officer. “And then I got up, and I saw the terrible scene.”
The Taliban took responsibility for the attack in a posting on its Web site, saying the group had dispatched a young man named Nizamuddin, a resident of Kabul. The Taliban said that Nizamuddin’s bomb weighed more than 1,600 pounds.
Bombers who have struck in the past have sometimes cruised the capital looking for targets, holding off on the detonator before they have found their marks. Intelligence officers often receive reports that car and suicide bombers have entered Kabul, some of them with no particular targets in mind.
That may have been the case Tuesday morning, when Nizamuddin, if that was his name, steered his minibus into the line of American cars. But even so, the attack came at what turned out to be a highly symbolic moment: just as President Hamid Karzai was preparing to meet the Afghan and foreign news media only hours after his return from Washington, where he had met with President Obama and other senior American officials.
Among the topics discussed in Washington was the Kandahar offensive, aimed at breaking the Taliban’s hold on southern Afghanistan. Afghan and American officials have said that they expect the Taliban to try to counter the operation in any way that they can.
It was the worst attack in Kabul in weeks. The insurgency is a largely rural phenomenon in a largely rural country, and on most days the capital is calm. The peace in the city, such as there is, is kept almost entirely by the Afghan police and army, with the Americans and NATO standing back.
While the Taliban were quick to congratulate themselves for killing the American and NATO soldiers, their statement made no mention of the dead and wounded Afghan civilians. The attack was condemned by the United Nations, NATO and the American Embassy, which accused the Taliban of “callous disregard” for the lives of ordinary Afghans.
The bomber struck at 8 a.m., when the streets were filled with traffic. The American convoy, which contained a number of armored S.U.V.’s, was moving down Dar-ul-Aman Road on the southern edge of the city. The road leads up a hill to the Afghan Counterinsurgency Academy, one of the principal centers for teaching tactics to Afghan officers and enlisted men.
The explosion sent a plume of fire into the air and ignited the cars and buses all around.
As the chaos unfolded, ambulances converged on the scene, and a pair of Black Hawk helicopters swooped in to take away the dead and wounded NATO soldiers.
“People were calling, ‘Help me, help me,’ ” said Yusuf Tahiri, an ambulance driver who carried off six dead and two wounded Afghans. “There were body parts everywhere.”
As Mr. Tahiri spoke, an Afghan soldier appeared, carrying a large red trash bag. It was, he said, filled with human brains. “What do you want me to do with this?” he asked. “Do you want me to bury it, or do you want to take it?”
The driver nodded, and the soldier walked around to the back of the ambulance and tossed the bag in the back.
“I have seen so many of these — so many,” said Mr. Tahiri, the driver, shaking his head.
The blast also flung people and wreckage over into the courtyard of a veterinary clinic of Kabul University. With the mayhem still unfolding, two Afghans, both of them guards at the clinic, sat on the curb and talked.
“I saw something just like this 10 years ago,” Mohammed Hussein said to his friend. “A rocket landed next to my house. Just like this.”
His friend, Abdul Hafiz, gave a weary nod.
“It was very dangerous, very horrible,” he said.
A car bomb attack this morning, which targeted a NATO (North Atlantic Treaty Organization) convoy in Kabul, the capital of Afghanistan, has killed or wounded dozens of people. The death toll was not confirmed, and estimates range from ten to twenty deaths. 47 people were injured in the attack.

The incident occurred at the Darulaman crossroads, near a US-Afghan military base and the parliament. Six NATO troops died in the attack alongside several civilians. The NATO said they had sealed off the region. The bomber had been driving a car filled with explosives, which they detonated at around  0815 local time 0415 GMT.

Iain Baxter, a spokesman for Isaf (), stated: "An Isaf convoy was hit. At the moment we're trying to confirm the number of Isaf casualties." He could not confirm the number of Isaf personnel killed in the attack.

Zemarai Bashary, an Interior Ministry spokesperson, confirmed the attack, noting that "there are a number of casualties, civilians killed and wounded." The death toll is unclear, and we're checking all the hospitals," he added.

Hamid Karzai, President of Afghanistan, said it was a "heartbreaking" attack. "We are condemning the attack in the strongest terms. I hope Afghanistan will soon get out of this suffering, God willing," he commented on national television.

General Ahmad Zia Yaftali, the chief military doctor of the Afghan army, claimed twenty people had been killed. "We have five bodies brought to our hospital so far ... the number of the dead is more than 20," Yaftali told Agence France-Presse news agency.

Later, the Taliban claimed responsibility for the attack, saying a resident of Kabul, Nizamuddin, had been sent to "destroy five foreign vehicles and damage one more." "Today's attack was part of the Al Fatah operation and we will continue attacking foreigners and government security forces and their associates," Zabihullah Mujahid, a Taliban spokesperson said. The latter had 1,500 pounds of explosives in his Toyota van. NATO officials said five US military convoys were destroyed along with a further thirteen public vehicles. One of the vehicles to be destroyed was a bus filled with people.