From left to right: Pte. William Cushley, Warrant Officer Frank Mellish, Warrant Officer Richard Nolan and Sgt. Shane Stachnik. An incident report by a U.S. military unit suggested they died by friendly fire in Afghanistan in September 2006, which the Canadian military says is untrue. (DND)

Rick Hillier, Canada's former top soldier, is questioning the accuracy of a leaked report that suggests four Canadian soldiers who died in September 2006 in Afghanistan were killed by "friendly fire" from U.S. forces.

Hillier, who was chief of the defence staff until his retirement in 2008, told CBC News on Tuesday that the Canadian military had an entire battle group in the area at the time and "knew very clearly what was going on."

Killed were Warrant Officer Richard Nolan of Newfoundland, Warrant Officer Frank Mellish of P.E.I. and Nova Scotia, Sgt. Shane Stachnik of Alberta and Pte. William Cushley of Ontario.

"We were certain, based on the enormous number of soldiers and sailors and airmen and airwomen that we had in that fight, what occurred that day," Hillier said in an interview with CBC News in Ottawa at the start of a cross-Canada charity motorcycle tour.

"Of course, this doesn't make it easier for the families when erroneous reports like this come out and they're trumpeted."

Rick Hillier served as chief of the defence staff until his retirement from the Canadian Forces in 2008. (Reuters)

The Canadian military is offering counselling to the four soldiers' families to help them cope with the leaked information.

Sgt. Stachnik's mother, Avril Stachnik of Waskatenau, Alta., said Tuesday she was outraged when she first heard the friendly-fire claim.

"It's a lie, for starters," she said. "I talked personally to some of his friends, and this is not how it happened."

According to an incident report filed by the U.S. military unit leaked over the weekend by the website WikiLeaks, four Canadian soldiers were killed and seven others and an interpreter were wounded on Sept. 3, 2006, when a jet dropped a bomb on a building they occupied during the second day of Operation Medusa.

The veracity of the WikiLeaks document hasn't been determined. The U.S. Pentagon would not comment on the leaked documents, including the friendly fire report.

The Canadian military says it has not been misleading about Canadian deaths and maintains the four soldiers died in combat with the Taliban.

NDP's Layton calls for transparency

In an interview Tuesday, NDP Leader Jack Layton said detail in the leaked report "undermines the confidence" Canadians have in the information provided to them by the government and called on politicians to "get to the bottom of it."

"We've got two very different accounts of how four of our troops were killed," Layton told CBC News in Toronto.

Layton said Prime Minister Stephen Harper's Conservative government has already shown an unwillingness to disclose information about Afghan detainee transfers, despite allegations the detainees faced torture at the hands of Afghan officials.

"I think there's a lot of concern about transparency and openness with this government, so here's an opportunity to have transparency," Layton said.

But Hillier said the U.S. military, like any bureaucracy, produces millions of documents, including "some written by people as first response who don't know what they're talking about and have the facts wrong."

"When I was a commander on operations, we always had a rule — first reports are wrong, and the second reports are wrong and the third reports are wrong," Hillier said.

"Only after that do you start to get the validity and the truth [to] come out."

However, Janis Karpinski, a former U.S. brigadier general, countered that the initial incident log is more valid than subsequent reports.

"When it's convenient, when it is politically correct … you're not going to get the truth as the conversations develop," she said.

"They're going to be coaching you in the direction they want you to respond over time. That's why those logs are so critically important. Because they do contain the truth. That's the first response — the event as it's being reported as it's happening."

Karpinski, who was the commanding general of Abu Ghraib during the scandal over the abuse of prisoners at that U.S.-run facility, has claimed the U.S. army made her a scapegoat. Although she was not directly implicated in the abuse, a report blamed her for not fulfilling her leadership role.