Published: May 18, 2010 12:24 PM EDT

KABUL, Afghanistan (AP) - A Taliban suicide car bomber struck a

NATO convoy in the Afghan capital Tuesday, killing six troops, five

of them American, officials said. Twelve Afghan civilians also died

- many of them on a public bus in rush-hour traffic.

The powerful blast occurred on a major Kabul thoroughfare that

runs by the ruins of a one-time royal palace and government

ministries. It wrecked nearly 20 vehicles, including five SUVs in

the NATO convoy, and scattered debris and body parts across the

wide boulevard. The body of woman in a burqa was smashed against

the window of the bus.

The attack - the deadliest for NATO troops in the capital since

September - comes despite a ramped up effort by Afghan authorities

to intercept would-be attackers and better secure a capital city

that saw a spate of brazen attacks this winter.

In the last such attack in February, suicide bombers stormed two

small downtown hotels and killed 16 people.

Taliban spokesman Zabiullah Mujahid told The Associated Press in

a phone call from an undisclosed location that the bomber was a man

from Kabul and his car was packed with 1,650 pounds (750 kilograms)

of explosives. The target of the attack was the foreign convoy, he

said.

U.S. troops and Afghan police held a security cordon around

wrecked vehicles at the blast site in the west of the city.

Emergency workers zipped the dead into body bags and lifted the

injured into ambulances.

"I saw one person laying on the ground with no head," said

Mirza Mohammad, who was on his way to work when the blast happened

up the road.

Police officer Wahidullah, who goes by one name, said he saw the

body of woman in a burqa smashed up against the window of the bus.

"Everywhere was dead bodies," Wahidullah said. At least 12

Afghan civilians died and 47 were wounded - most of them in the

bus, the Interior Ministry said.

NATO said six of its service members were killed in the attack,

and U.S. forces spokesman Col. Wayne Shanks confirmed that five of

those were American. The nationality of the sixth was not

immediately disclosed.

It was the deadliest attack for NATO in the capital since a

September suicide bombing that killed six Italian soldiers. The

attack comes as NATO readies a major offensive in the southern

province of Kandahar, a major Taliban stronghold.

NATO Secretary-General Anders Fogh Rasmussen condemned the

attack and said it would not deter NATO's efforts in Afghanistan.

"NATO remains committed to its mission to protect the Afghan

people and to strengthen Afghanistan's ability to resist

terrorism," Rasmussen said in Brussels.

President Hamid Karzai also condemned the attack.

"There were casualties among the NATO forces as well as among

civilians - women, children and schoolchildren," Karzai told a

news conference.

NATO said that five of its vehicles were damaged as well as more

than a dozen civilian vehicles. There were no obvious military

vehicles among the wreckage, but NATO troops often travel in

unmarked SUVs in the capital.

The Feb. 26 attack against two residential hotels in the capital

killed six Indians, along with 10 Afghans. Afghan authorities

blamed the attack on Lashkar-e-Taiba, the same Pakistan-based

Islamist militia that India blames for the 2008 Mumbai terrorist

attacks that killed 166 people.