Prime Minister Stephen Harper has waded into the debate over Canada's non-combat mission in Iraq sparked by news that Canadian special forces troops recently returned fire from ISIS fighters while accompanying Iraqi troops near the front lines.

"This is a robust mission, we're there to make those guys effective so they can take on the Islamic State and deal with them," he said in response to a question from CBC News during an appearance in St. Catharines, Ont.

"If those guys fire at us, we're going to fire back and we're going to kill them, just like those guys did — and we're very proud of them."

Harper's comments come as his top general sought to clarify his views on the mission's parameters.

Prime Minister Stephen Harper says if Canadian troops come under fire by ISIS, 'we're going to fire back and we're going to kill them.' (Nathan Denette/Canadian Press) Acknowledging the situation on the ground in Iraq has "evolved" since last fall, Chief of Defence Staff Gen. Tom Lawson said the activities of the Canadian special operations team deployed against ISIS are "entirely consistent" with its original mandate from the government.

Last October, Lawson told CTV's Question Period host Robert Fife that Canadian troops sent to advise Iraqi and Kurdish forces battling ISIS "would have nothing to do" with pinpointing targets for airstrikes.

"All coalition troops on the ground in Iraq are being used in the same role — advise and assist, but not accompany, and not engage in direct combat," Lawson said last October. "It's very important that it's Iraqi soldiers who do that."

He also agreed that helping out with laser targeting would be a "semi-combat role."

But in a briefing to reporters this week, Brig.-Gen. Mike Rouleau said his soldiers have directed 13 airstrikes in the region using laser pinpointing. He said Canadian soldiers did the work because the Iraqi soldiers cannot, and that it did not mean Canada has escalated its mission.

Rouleau said Canadians' involvement in targeting had the added benefit of giving commanders confidence that the targets are legitimate, making the process faster and safer not only for local troops, but civilians as well.

In a written statement issued Thursday, Lawson confirmed Canada has "increased our assistance with respect to targeting airstrikes," which, he stressed, was "in direct correlation with an increased threat encountered by the ISF [Iraqi Security Forces.]

"To be clear, the situation on the ground has evolved since I offered those remarks" in October, he added.

Although Canadian special operations forces "are not seeking to directly engage the enemy," Lawson said, they are "providing assistance to forces that are in combat."

'Ground combat' ruled out?

Earlier this month, Canadian special forces operators came under fire while travelling near the front lines as part of a training operation.

Chief of Defence Staff Gen. Tom Lawson acknowledged that the situation on the ground in Iraq has 'evolved' since last fall. (Justin Tang/Canadian Press) News of the firefight, which was revealed by mission commanders Jonathan Vance and Michael Rouleau during a briefing Monday, sparked a debate over whether Canada had quietly expanded its efforts in Iraq to include a combat role.

The resolution passed by the House of Commons last year explicitly ruled out ground combat operations.

Both the New Democrats and the Liberals have accused the government of not being honest about the extent of the mission.

Lawson said in his statement Thursday the defensive action was "entirely consistent with the advise and assist mandate given to the Canadian Armed Forces by the government."

He added: "You should be justifiably proud of your men and women in uniform."

'We haven't done anything that we shouldn't be doing': Nicholson

Defence Minister Rob Nicholson, who is in London at a high-level meeting on the anti-ISIS efforts, fielded questions on the newly revealed role during a teleconference on Thursday morning.

"We haven't done anything that we shouldn't be doing," he said, pointing out Canadian Forces have a "long tradition going back 200 years" of returning fire when under attack.

"That's part of our special operations forces on the ground," he added.

"That advise and assist role has been supported by the government and approved by Parliament."

He noted Canadian troops have also been conducting airstrikes out of Kuwait.

"This comes with government acceptance and parliamentary acceptance as well," he told reporters.

Neither the New Democrats nor the Liberals backed the resolution establishing the parameters of mission when it came before the House last fall. It nevertheless passed easily due to the Conservative majority.

Earlier, Nicholson told CBC News Network host Heather Hiscox that any extension of the mission "would be a decision of the government," but would also be brought back before Parliament.

Canadians 'misled' about mission: NDP

Before that happens, however, Nicholson will have to field a few pointed questions from the other side of the Commons when the House reopens for business next week.

"I think it's very much incumbent on the minister and the prime minister to explain why Canadians were misled about the nature of this mission," New Democrat defence critic Jack Harris told CBC News.

"There's lots of contradictions between what Gen. Lawson said today, and what he's said before, and what Mr. Nicholson has said before, and what Mr. Nicholson said today that he'd said before — and there's a tremendous amount of confusion in the public mind," he noted.

"If you go back to the official record … to what the prime minister said in the House of Commons, it was very clear that the kind of things that were reported as having happened last week were not contemplated by Canadians, by Parliament or by the prime minister, if you take his comments literally."

Harris said it's "pretty clear" that this sort of participation on the front lines — including having special forces operators calling in "over half the airstrikes" — was not what was discussed in the House last September.

"That's something we'll certainly be raising next week."

Liberal defence critic Joyce Murray said Lawson's latest statement reflects "a very different reality" from what has been coming from either the defence minister or the prime minister.

"The minister is saying there was no change, and it was always intended to be 'advise and assist,' but now the [chief of defence staff] is saying there has been a change," she told CBC News.

"Is the minister telling the truth?" she wondered.

"And if not, why was there no notice to Parliament and the public about this very significant change?"

Murray said her party has repeatedly asked for additional briefings on the mission, "just so if there was a change in circumstances, the government could undertake its responsibility to keep us informed," she said.

"Now they're scrambling."