KABUL, Afghanistan — As Afghan President Hamid Karzai was preparing Tuesday to trumpet the success of his recent meetings in Washington, a suicide bomber in Kabul killed 18 people — including five U.S. troops — a grim reminder that the capital is still a prime target for Taliban insurgents.
The bomber, driving more than a half-ton of explosives, targeted a NATO convoy in busy early morning traffic on a chaotic, pothole-riddled artery into the city center.
The blast blew armored SUVs aloft, ravaged a crowded bus and sent shrapnel flying hundreds of yards in the most jarring attack on the Afghan capital since February.
Five American fighters, a Canadian soldier and 12 Afghan civilians died in the attack, officials from the three nations said. It was the worst U.S. military loss since last October, when a roadside bomb killed seven soldiers in southern Afghanistan, carrying the American death toll in the war to 1,000, according to iCasualties.org, which tracks casualties in Afghanistan and Iraq.
Within hours, the Taliban claimed credit for the blast, which hit as Karzai was preparing to hold a news conference to drive home the message that he and President Barack Obama are united as they face a crucial summer.
Hours later, Karzai condemned the attack before he spoke to the news media about his fence-mending trip to the United States.
Karzai is preparing to host a nationwide assembly to debate the conditions for talking with the Taliban. The Obama administration is sending more U.S. troops to Afghanistan in preparation for a critical summer: American officials are looking to cripple the Taliban and weaken their position at the negotiating table.
One witness said the explosion decimated the bus, "splitting" one burqa-clad woman in half.
"The blast was so powerful you couldn't find the vehicle," said a police investigator who declined to give his name as he rushed from the scene.
The convoy was hit as it approached the eerie ruins of former King Amanullah Khan's palace, a war-ravaged, abandoned hilltop citadel that's become a reminder of the country's decades of war.
The attack occurred in a sprawling area that includes an Afghan army training center, the parliament and the U.S. military's counterinsurgency academy, a school designed to further the military doctrine that focuses on protecting civilians instead of killing insurgents.
Investigators said the bomb probably weighed more than 1,200 pounds, and it left a crater about 9 feet wide and 3 feet deep.
Tuesday's assault followed a nationwide sweep in which the Afghan government said it had arrested more than 115 suspects, including would-be suicide bombers planning attacks on the capital.
Two weeks ago, Afghan officials announced the arrests of 16 suspects who they said were planning suicide and rocket attacks on Kabul.
Witnesses said that Tuesday's car bomb hit as the NATO convoy was navigating the busy street just after 8 a.m. local time.
"One of the vehicles was thrown from one side of the road to the other," said Bashir Ahmad, a 22-year-old who runs a small fuel shop across the road from the blast site.
At the scene, U.S. soldiers covered one victim with a camouflage blanket until they could move the body, which lay outside a ravaged Suburban that was part of the NATO convoy.
The Afghan bus, its windows shattered, stood empty a few feet from the bomb crater. The blast destroyed at least a dozen vehicles. Blood seeped into the dirt median near a yellow taxi that the explosion had thrown onto its side.
The bombing was another sign that Afghan insurgents are able to strike Kabul and keep its residents in a state of anxiety.
It was the most devastating attack in the capital since late February, when insurgents staged a coordinated assault on two small hotels. Attackers who used a car bomb and automatic weapons killed 16 people, including an Italian diplomat, a French filmmaker and six Indians who were working in Afghanistan.
Afghan investigators have blamed that attack on Islamist militants who are thought to be helping Pakistan challenge India's political influence in the region.
(Shukoor is a McClatchy special correspondent.) MORE FROM MCCLATCHY U.S. embrace of Karzais brother disappoints many Afghans
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