An investigation is underway after a warning shot fired by a Canadian soldier wounded two Afghan bystanders in Kandahar, while Prime Minister Stephen Harper described military operations in the country as "war."

"The fact of the matter is, we are engaged in a war in Afghanistan," Harper told a radio show on Saturday. "We have been for some years, but we are today at the front lines of that war."

In the past, military and government officials have preferred to describe the Afghanistan mission as combat operations in support of aid and reconstruction.

NDP Leader Jack Layton said the mission should have been described as a war from the start.

"(They) should have been telling the upfront truth to Canadians from the beginning. When we suggested it was a war, any Canadian who said so was pushed aside," Layton told CTV News.

On Saturday, soldiers were running a resupply convoy through Kandahar city when a vehicle got too close, prompting a warning shot from a Canadian soldier.

The vehicle's occupants were not injured, but shrapnel struck two bystanders.

A 16-year-old boy walking nearby was hit in the leg, and a man on a motorcycle was hit in the stomach and neck.

The pair were taken to a local hospital and their injuries are not believed to be life threatening. The boy underwent surgery late Saturday to remove a piece of bullet from his leg.

The boy's father questioned why Canadians hurt Afghan civilians in their efforts to stay safe from suicide and roadside bombs.

"This is not the way to operate, my boy has done nothing,'' Faeed Ifaq told The Canadian Press as he waited for his son to wake up following surgery.

CP reports that Ifaq then pulled a bullet from his pocket that he claimed struck his son while he was riding a bicycle.

Canadians have fired warnings at several Afghan civilians and allies in recent months, killing a police officer, a young boy and a taxi passenger.

Military officials said, in each case, soldiers were following procedure and responding to a perceived threat.

"These do happen from time-to-time, but I'm not sure it would be fair to say there has been an increased amount of them," said navy Lt. Sue Stefko, a spokesperson for the Canadian mission in Afghanistan.

"It just happens that some people do not obey the rules that we ask them to."

Officials wouldn't say what warnings were delivered before the shot was fired Saturday.

Meanwhile, NATO is appealing to allies to urgently provide up to 2,500 troops for the battle with Taliban insurgents in southern Afghanistan. On Friday, reports emerged that Canada will send tanks and increase its contribution of troops by about 200.

British Lieutenant General David Richards, commander of NATO forces in the war-torn country, said the fight against the Taliban could last for another five years. Canada has pledged to continue military operations in Afghanistan until 2009.

But Richards told Britain's Channel 4 News that beating insurgents is possible, and they will soon "start dancing to my tune."

Friendly-fire

Sources have told The Globe and Mail that a blazing garbage fire lit by Canadian forces may have been at the centre of a friendly-fire incident that killed one soldier and wounded 30 others in Afghanistan.

The Globe quotes a military officer who says the pilot of a U.S. Warthog plane opened fire after being ordered to target a blaze at a suspected Taliban position along the Arghandab River on the morning of Sept. 4.

The fire was right in the pilot's flight path, and the pilot apparently mistook the Canadians for the intended militant target.

Sources also told The Globe the American pilot realized the error almost immediately and ceased fire. But it was too late, as cannon fire from the A-10 Warthog's seven-barrel Gatling gun had already hit the Canadian troops' encampment.

An investigation meanwhile continues into the sequence of events that led to the deadly incident that killed Pte. Mark Anthony Graham, a member of 1st Battalion, The Royal Canadian Regiment.

Senior military officers not party to the investigation said while their knowledge is limited, a general picture of the accident is emerging. Bad coincidence and failure to achieve 100-per-cent confidence in target identification before firing contributed to the fatal fire, the sources said.

With a report by CTV's Roger Smith and files from The Canadian Press