Click here to find out more! 5 Americans among 18 killed in Afghan suicide blast

Reporting from Kabul, Afghanistan
Shattering a nearly three-month hiatus on attacks in the Afghan capital, a suicide bomber driving a minivan packed with explosives struck a Western convoy on a busy road Tuesday. The powerful blast killed at least 18 people, including five American service members.

A sixth foreign soldier, whose nationality was not immediately disclosed, also was killed.

The explosion occurred at 8 a.m., when many people were on their way to work. A crowded Afghan passenger bus was caught up in the carnage, with many aboard killed or injured.

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The massive blast carved a deep crater in the road in the shadow of a ruined imperial palace on Kabul's western edge, overturning cars and scattering shrapnel and body parts over a wide area. The thunderous echo reverberated across much of the city; police said all that was left of the attacker's vehicle was the engine block.

"Pieces of people covered the road — heads and hands and limbs," said a 73-year-old guard named Osain, who worked at nearby Kabul University.

The convoy consisted of unmarked armored SUVs, often used to transport military officers and diplomats around the city. One was flipped end over end by the force of the explosion, and the one behind it was reduced to a scorched hulk. Five military vehicles in all were damaged, along with more than a dozen civilian ones.

NATO, the U.S. Embassy and the European Union condemned the attack, in which — like many bombings targeting convoys or military installations — noncombatants took the brunt. Afghanistan's Interior Ministry described 12 of the dead as "innocent civilians" and said nearly 50 other people, mainly passersby, were hurt.

"This sort of desperate brutality and aggression reminds us of the pessimism of an enemy who seeks to kill the innocent and stop the progress necessary for a better Afghanistan," NATO's International Security Assistance Force said in a statement.

The Taliban claimed responsibility for the bombing, which marked the first major attack in the capital since February, when assailants killed 16 people in a strike against two small guesthouses. Security has been tightened in the wake of that incident, but bombers routinely penetrate even the most heavily guarded precincts of the capital.

An attack like Tuesday's would have been difficult to plan in advance; Afghan and U.S. officials said the bomber likely cruised the area, aided by "spotters," before stumbling upon a prime target.

The bombing came shortly before President Hamid Karzai held a news conference in which he portrayed his trip last week to the United States as an opportunity to press the Obama administration to reduce Afghan civilian casualties in the fighting between Western troops and insurgents. The trip followed months of tensions between the two governments.

Tuesday's attack left many residents feeling rattled and insecure. Afghans often complain that the government seems incapable capable of preventing insurgent strikes in the heart of Kabul, although police often tout the breaking up of suicide cells and the capture of other would-be attackers.

"Such things are inhuman," said 27-year-old university student Fazel Ahmad. "Attacks like this are such an affliction that people aren't safe in Kabul. We can't walk free."