The Taliban has claimed responsibility for a suicide bombing in Kabul that killed 18 people -- including the highest ranking Canadian officer to die in the war since it began in 2002.

A vehicle containing hundreds of kilograms of explosives drove into a NATO convoy during the city's busy morning rush hour and exploded.

The bomb killed Canadian Col. Geoff Parker, five U.S. soldiers and 12 Afghan civilians. Nearly 50 people were wounded, most of whom were civilians.

It was the most lethal attack in Kabul since late 2009.

Parker, 42, was once the commanding officer of the 2nd Battalion of the Royal Canadian Regiment. He was raised in Oakville, Ont., and was based at Land Force Central Area Headquarters in Toronto.

He had travelled to Kabul to take part in an upcoming mission, said Col. Simon Hetherington, deputy commander of Task Force Kandahar. The nature of that mission hasn't been disclosed.

Hetherington described Parker as "a rising star" whose "potential was undeniable."

Condemning the bombing, NATO Secretary-General Andres Fogh Rasmussen said the violence would not deter members from their mission.

"NATO remains committed to its mission to protect the Afghan people and to strengthen Afghanistan's ability to resist terrorism," Rasmussen said in Brussels.

The attack was also the deadliest that NATO troops have suffered in Kabul so far this year. It wrecked nearly 20 vehicles, including five SUVs in the NATO convoy.

"I saw one person lying on the ground with no head," said Mirza Mohammad, who witnessed the explosion on his way to work.

Taliban spokesperson Zabiullah Mujahid claimed in a telephone interview with The Associated Press that the bomber was from Kabul and carried 750 kilograms of explosives in his car.

The bomber had been targeting the NATO convoy, Mujahid said.

But Brig. Gen. Josef Blotz, a spokesperson for NATO's International Security Assistance Force, said it would have been difficult for the bomber to tell a NATO convoy from United Nations or a private security contractor's convoy.

"I would call it a target of opportunity," he told CTV News Channel. "For security reasons we tend to change cars, to change routes in the city. We change tactics, procedures and techniques in order to avoid these dangerous situations."

From Kandahar, Canadian Press reporter Tara Brautigam said the blast shattered any perceptions that Afghanistan's capital city is secure.

"Kabul, up until the past year or so, was seen as one of the more peaceful, relatively stable cities in the country," he said by phone. "But I think as of late, and particularly this incident, has removed that veneer of stability."

The bombing was the first major attack in Kabul since February. Since then, however, the Taliban has announced a spring offensive.

"It is a grim milestone," Brautigam said, because of the high rank that Parker held.

According to Parker's official Department of National Defence biography, he was a career solider who signed up for the military in 1989 when he was a student at the University of Western Ontario.

After graduating from UWO with an undergraduate degree in engineering science, Parker earned two master's degrees -- one in electrical engineering, the other in defence studies -- from the Royal Military College.

Parker was a married father of two children. Originally from Oakville, Ont., he is the 145th Canadian soldier to be killed during the war in Afghanistan.

Two civilians -- diplomat Glyn Berry and Calgary Herald journalist Michelle Lang -- have also died.

With files from The Associated Press and The Canadian Press