Canada's top general acknowledged Thursday that the country's military mission in Iraq has “evolved,” but continued to deny that Canadian soldiers are engaged in a combat mission against Islamic State militants.

Gen. Tom Lawson came under heavy questioning from opposition MPs during an appearance before a House of Commons committee Thursday, saying that certain actions "can appear in any mission" to appear to be combat.

Senior military officials revealed earlier this month that Canadian special forces have come under fire from ISIS militants three times and have returned fire. Commandos are also identifying targets for coalition airstrikes, even though Lawson told CTV's Question Period in October that special ops would do no such thing.

On Thursday, Lawson took responsibility for the decision to allow Canadian commandos to identify targets for airstrikes, telling the committee that he did not foresee the need for such action when he made his comments on Question Period.

The special forces' advise and assist training mission was going so well, however, that they were able to move on to teaching how to identify airstrike targets.

"So, in fact I provided them, within the advise-and-assist mission, the authority to go ahead with that," Lawson said.

The military only revealed earlier this month that Canadian commandos have been guiding in airstrikes since late November.

Lawson told the committee that a combat mission "is very different" than what special forces have been doing on the ground.

"It would use us directing our fire power against ISIS, which is not what we have the mandate to do," Lawson said, noting that special ops have defended themselves when they have come under enemy fire.

There are approximately 69 Canadian special forces in northern Iraq, training Iraqi forces in their fight against ISIS militants.

Defence Minister Rob Nicholson told the committee Thursday that "it has been an evolutionary process" assisting Iraqi forces with "strategic and tactical planning."

But the fact remains, he said: "This is not a combat mission."

Conservative MP Laurie Hawn asked Lawson whether a sniper's individual rounds would not fall under the definition of a firefight.

Lawson responded that while he is "not sure of that," it does not fall into the definition of combat.

The opposition was incensed at the seeming parsing of words.

"When you have soldiers on the ground, on the front line, whether you call it a combat mission or not, it is combat," NDP foreign affairs critic Paul Dewar said at committee.

Meanwhile, the opposition also demanded to know the cost of the Iraq mission. The Pentagon estimates that the cost of the U.S. contribution to the coalition will top $1 billion.

Nicholson said the cost remains a moving target, but MPs can expect to see the figures in public accounts records to be released later this year.

With a report from CTV's Ottawa Bureau Chief Robert Fife and files from The Canadian Press