Two Canadian aid workers and a British colleague held hostage in Iraq were freed Thursday during a rescue operation mounted by coalition forces, including elite Canadian commandos, ending the four-month hostage ordeal that saw their American colleague killed.

The freed aid workers include Canadians James Loney, 41, and Harmeet Singh Sooden, 32, and Briton Norman Kember, 74.

CTV News has learned that Canada's elite JTF-2 special forces were instrumental in helping to rescue the three aid workers.

Though Prime Minister Stephen Harper said Canada participated in the operation, he wouldn't confirm nor deny reports that the top secret commandos helped rescue the aid workers.

"At every phase of these particular events of this hostage-taking, Canadian government officials, the government of Canada, was fully engaged," Harper told reporters in Gatineau, Que.

"Anything beyond that, I'm afraid I'm not at liberty to say. These are issues of national security," said Harper, who was awakened in the early hours with news of the rescue.

Foreign Affairs Minister Peter MacKay confirmed Thursday several Canadian agencies were involved in the rescue, including the Department of National Defence, the Canadian Security Intelligence Service and the RCMP.

"From top to bottom, in all the departments, everyone has been on the file, on the job," he said, appearing on CTV Newsnet's Mike Duffy Live.

The freed hostages are currently at the British Embassy in Baghdad's Green Zone following a brief checkup in hospital.

Fellow member of the Christian Peacemaker Teams Anita David said the men had lost a lot of weight but they had not been physically mistreated by their captors.

"This was one of those moments of complete relief and a great deal of pleasure in seeing one another," David told The Canadian Press from Baghdad after being reunited with her colleagues.

"Loney was grinning from ear to ear."

The two Canadians exercised daily, with Loney doing stretches while Sooden did sit-ups and ran up and down stairs.

Their happy release was tempered with news of something they had been dreading -- confirmation that their colleague 54-year-old American Tom Fox had been killed.

Fox's bullet-riddled body was found on a Baghdad street on March 10, just days after his captors released a video in which he was ominously missing.

British Embassy spokeswoman Lisa Glover told The Associated Press the men are expected to be flown out of Baghdad in the next few days.

Loney, a longtime housing activist in Toronto, is expected to return to Canada in the next few days.

Sooden's brother-in-law Mark Brewer said relatives planned to travel to Baghdad to bring him home.

The four aid workers -- all members of the Christian Peacemaker Teams -- were kidnapped Nov. 26 at gunpoint on a Baghdad street.

Just a few days later, a previously unknown group calling itself the Swords of Righteousness Brigades claimed responsibility for the abduction in a videotaped aired on the al-Jazeera television network.

In a second videotape released Dec. 2, the group threatened to kill the hostages by Dec. 8 if all Iraqi detainees were not released from U.S. and British detention facilities by Dec. 8.

The deadline was later extended to Dec. 10, but it passed without word on the fate of the aid workers.

The last time the four hostages were seen together was in a silent videotape broadcast on al-Jazeera on Jan. 28. A voice-over on the tape called it the "last chance" for authorities to release Iraqi prisoners.

A videotape broadcast on al-Jazeera on March 7 did not show Fox. The other three aid workers were shown apparently calling on their governments to help them.

At least 235 foreigners have been taken hostage in Iraq and nearly 40 have been killed over the past two years. Most have been released, although a number are still missing.

With a report from CTV's Tom Kennedy and files from The Canadian Press