Canada's opposition leader accused Prime Minister Stephen Harper on Tuesday of having lied when he promised no ground combat alongside airstrikes against the Islamic State group in Iraq.

The accusation comes after Canadian special forces exchanged gunfire with Islamic State fighters in the Mideast country in recent days, in the first confirmed ground battle between Western troops and IS.

The Canadians came under mortar and machine gun fire while training Iraqi troops near front lines and shot back in what Canadian special forces commander Brigadier General Michael Rouleau described as self-defense, killing the IS fighters.

No Canadians were injured in the clash.

Opposition New Democratic Party leader Tom Mulcair pounced on the news, saying Harper had "told Canadians that they would not be involved in combat. He did not tell the truth."

Harper's spokesman, Jason MacDonald, was unapologetic, telling AFP that the "international jihadist movement has declared war on Canada and its allies."

"We must face this threat directly, and that's exactly what this government is doing," he said, adding that the ruling Tories "support 100 percent" its troops fighting IS in Iraq.

Harper had asked parliament in September to support joining the international coalition launching air strikes on the Islamic State group.

Both the opposition New Democrats and Liberals voted against the mission in the House of Commons, saying they feared it could become a quagmire.

But Harper's Conservative majority carried the vote in favor of a six-month mission, while ruling out sending ground combat troops.

Canada sent some 600 air crew and other military personnel -- as well as six fighter jets and other military aircraft -- to the region in November to participate in the air strikes.

Sixty-nine special forces were also tasked with training Iraqi troops.

Rouleau told a media briefing on Monday that special forces have also lighted targets in Iraq for coalition aircrafts to strike.