KANDAHAR, Afghanistan — Two unarmed Afghan civilians were shot and killed by NATO forces in a pair of bizarre, seemingly unrelated, incidents Saturday.

One episode, 12 kilometres west of Kandahar, involved a Canadian battle group patrol and a man the army implied may have been mentally unstable.

Separately, unidentified alliance troops opened fire and killed a second man who ran in between vehicles of a parked convoy in the pre-dawn hours, near Kandahar Airfield.

The early-morning incident did not involve Canadians and military officials declined to say what nationality they might be.

"There were two incidents today, very similar sounding in nature,'' said Lt.-Cmdr. Kris Phillips, a spokesman for the Canadian Forces.

"I can't speak about the first incident but the second incident involved us and took place on the highway out towards the Zhari-Panjwaii area.''

For the Canadians, it is the second time in a week they've been involved in an unintentional shooting and both incidents Saturday join a long series events which have started to erode relations with the Afghan population, who've taken to complaining bitterly about being in the crossfire -- or on the receiving end of stray warning shots.

Describing the man as a suspected suicide bomber, Phillips said the unidentified victim in the Canadian incident -- outside the village Senjaray --  approached a patrol, walking along the centre line of the road.

"He appeared to be chanting and refused to heed verbal and visual warnings to stop,'' Phillips said at Kandahar Airfield.

The closer the man came, the stranger he appeared and as the patrol slowed soldiers spotted what they thought were wires sticking from a bulge in the man's jacket.

Two warning shots were quickly snapped off but the man kept coming until a third burst was fired, killing him instantly.

"Upon closer investigation, no explosives were found but the man did have an unusual mix of wire, straps, tubes and other materials fastened to his torso,'' said Phillips, who added a military police investigation has been launched in conjunction with Afghan authorities.

"His behaviour is perplexing to say the least. We're not sure why he was in the middle of the road.''

"We're not sure why he was approaching one of our convoys. We're not sure why he was behaving the way he was, so there are some questions that need to be answered.''

In a puzzling coincidence, just before dawn, another Afghan man ran between the vehicles of a convoy stopped near Kandahar Airfield. A gunner on one of the vehicles flashed a light but the man kept moving toward the convoy and it was assumed he was a suicide bomber.

A warning shot went up but the man still kept coming, so soldiers opened fire on him directly.

The troops, whose nationality has not been released, called for explosive experts to see if the man was carrying a bomb before rendering first aid.

As it turns out, the second man was also not carrying explosives and he later died in the NATO hospital at the airfield.

In a statement, the alliance said it deeply regrets this loss of life.

NATO "forces attempted to warn the individual away from the convoy but he did not respond,'' said Lt.-Col Angela Billings, a military spokeswoman in Kabul.

Earlier this week, Canadian soldiers on a resupply convoy opened fire on an Afghan National Army convoy, wounding one officer. That incident apparently led to a short, tense standoff with Afghan soldiers.

Since deploying to the volatile southern region a year ago, Canadian troops have been involved in a total of three fatal civilian shootings, including the one on Saturday.