The death of a Canadian soldier and 16 others in a suicide bombing has brought into sharp focus the dangers that remain in Afghanistan even after the end of Canada's combat mission there.

Master Corporal Byron Greff, who was serving as a mentor and instructor to Afghan army trainers, was on a routine trip between training and headquarters in Kabul on Saturday morning when a car packed with explosives rammed into a heavily armoured NATO bus known as a Rhino.

Speaking after the close of the Commonwealth summit in Australia on Sunday, Prime Minister Stephen Harper expressed his regrets about the loss of the soldier but added he was well aware from his own travels in Afghanistan that safety is always a concern.

"I've always been clear there are still risks involved in this mission," Harper said.

"Any mission in Afghanistan involves significant risks .... Any presence in Afghanistan, as I know from my own travel there, is fraught with risk, so there will remain risk to our defence personnel."

Retired major-general Lewis MacKenzie, now a military analyst, expressed the hope that the tragedy would not be used against Canada's new mission which involves more than 900 soldiers training the Afghan army.

"Some people, especially critics, will react and say ‘We told you so,' but let's just keep this thing in perspective," he said, adding that the number of Canadian soldiers killed this year in Afghanistan is significantly lower than in previous years of the combat mission. Canada's combat role ended in July.

In expressing condolences to Greff's family, Harper said the young man had "paid the ultimate price serving his country."

"His life and death serves as an example of the bravery and outstanding dedication of Canadian Armed Forces members on this mission," the prime minister said in a statement.

He loved playing hockey

Greff, who was based in Edmonton with the reconnaissance platoon of the 3rd Battalion Princess Patricia's Canadian Light Infantry, was described by a senior officer as an "extremely fit" soldier who loved hunting and playing hockey in his free time.

"To say that he was highly respected by his fellow soldiers would be an understatement," Colonel Peter Dawe, deputy commander for the Canadian training mission, told reporters in Kabul.

"We will mourn the loss of our brother Byron but we will continue with the mission," he added. "This is a difficult time. The members of the task force remain steadfast in their focus and determination as they continue to help the people of Afghanistan work towards a safer and more peaceful future."

Greff, who was on his second tour of Afghanistan, was the 158th Canadian soldier to die in connection with the military's operations in that country.

Four other NATO soldiers and eight civilian contractors were killed in the blast. Four Afghans died and scores of others were wounded.

According to reports from the scene, the explosion happened as the convoy passed the American University in Kabul. The blast sparked a fireball that littered the street with shrapnel and filled the air with heavy black smoke.

Taliban targets Kabul

While Canada's new training role was expected to be safer for soldiers, Kabul has become a focal point for Taliban attacks. Last month, Canadian troops joined a 20-hour firefight near NATO's headquarters and the U.S. embassy.

"Afghanistan is a dangerous place," said Lieutenant-Colonel Christian LeMay, a spokesman for Canada's Ottawa-based overseas headquarters. "Precautions have to be taken and in this case precautions were taken. It was a bad attack."

Walter Dorn, an expert in peacekeeping and the Afghan conflict at the Royal Military College of Canada, said no mission, even for training, is without danger.

"The Canadian government calls it a non-combat mission, but there are cases where you might find your soldiers actually engaged in combat, if only for self-protection," he said.

In expressing his condolences to Greff's family, Governor General David Johnston praised the soldier for "answering the call to service with great integrity and courage."

"This sacrifice will not be forgotten," he said in a statement. "Canadians are united in sorrow at the death of one of ours."

Both NDP Leader Nycole Turmel and Liberal leader Bob Rae also expressed their condolences to the family of the dead soldier.

The death shows the continuing dangers in Afghanistan, Rae said, but "the training mission is probably the least risky of any potential presence in Afghanistan."

The commander of all Canadian troops overseas, Lieutenant-General Stuart Beare, says insurgents have been trying to undermine confidence in the Afghan government with their recent attacks.

"They are going to be trying to do this all of time," Lt.-Gen. Beare said an interview with The Canadian Press, conducted before Saturday's bombing. "They're not after territorial gain. They're going to continue to attack in the perception space and the idea that Afghanistan will never be safe."

With files from The Canadian Press