Three Canadian men who blame Ottawa for their alleged torture in Syria protested outside Prime Minister Stephen Harper's office on Thursday to demand that a secret probe into their case be opened to the public.

The peaceful demonstration added to pressure on Harper to help Moslem Canadians who are in trouble abroad because of supposed ties to militant groups such as al Qaeda.

Ahmad El Maati, Abdullah Almalki and Muayyed Nureddin were arrested separately when entering Syria between 2001 and 2003. They say they were tortured and interrogated, and some of the questions they were asked were based on information that could only have come from Canada.

"Mr Harper, I was detained in Syria. Why? I was tortured in Syria. Why?" Nureddin told a small crowd outside an entrance to the Ottawa building where Harper has an office.

The three men, seeking to clear their name, want to be able question witnesses and examine documents as the closed-door inquiry examines if officials dealt correctly with the trio.

The Conservative government ordered the probe in 2006 after an earlier public inquiry found that software engineer Maher Arar had been deported to Syria by the United States, and tortured there, after Canadian police falsely identified him as an Islamic extremist.

Government lawyers say the probe is looking at the conduct of officials rather than trying to clear the men's names. A report will released once the inquiry ends later this year.

"I want the Prime Minister to come down here and look me in the eye and explain to me why...the Canadian government subcontracted my torture to the Middle East," said El Maati, standing next to several hooded figures dressed in orange jumpsuits of the type worn by prisoners at Guantanamo Bay.

The only western prisoner still in the U.S. prison is Canadian Omar Khadr, who is accused of killing a U.S. soldier in Afghanistan in a 2002 firefight when he was just 15.

Critics say Harper should press for Khadr's return to Canada because he was so young when the alleged incident happened. Harper refuses to do so, saying Khadr is accused of a very serious crime.

Ottawa is also under fire for the way it is handling the case of Abousfian Abdelrazik, a Canadian man taking refuge in the Canadian embassy in Sudan.

Abdelrazik, who Canada says is suspected of links to the Taliban and al Qaeda, says Ottawa is refusing to give him a passport and thwarting his bid to return home. He was jailed in Sudan in 2004 and is now free.

A secret Canadian government document obtained by local media says Sudan jailed Abdelrazik "at our request."