* Canadian-born Omar Khadr was held at military base
* Captured as 15-year-old fighting in Afghanistan
* Canada says transferred to Ontario prison (Updates with quotes, details)
The youngest prisoner and last Westerner held in the Guantanamo military base, Omar Khadr, was sent to finish his sentence in his native Canada on Saturday, the Canadian government said.
Canadian Public Safety Minister Vic Toews said that Khadr, who was a 15-year-old fighting in Afghanistan when captured in 2002, had been flown from Guantanamo Bay, Cuba, to a military base in Trenton, Ontario and transferred to the province's Millhaven maximum-security prison.
Khadr's case has been controversial both in Canada and abroad given his age when he was captured, the nature of his detention and hearing, and the reluctance of Canadian officials to accept his return.
"I am satisfied the Correctional Service of Canada can administer Omar Khadr's sentence in a manner which recognizes the serious nature of the crimes that he has committed and ensure the safety of Canadians is protected during incarceration," Toews said in Winnipeg, Manitoba.
A U.S. war crimes tribunal in 2010 sentenced Khadr, now 26, to 40 years in prison, although he was expected to serve just a few more years under a deal that included his admission he was an al Qaeda conspirator who murdered a U.S. soldier.
Khadr pleaded guilty in 2010 to charges that included murdering American Army medic Christopher Speer with a grenade in a 2002 firefight, conspiring with al Qaeda to commit terrorist acts, making roadside bombs to target U.S. troops in Afghanistan, spying on American military convoys and providing material support for terrorism.
Khadr was the first person since World War Two to be prosecuted in a war crimes tribunal for acts committed as a juvenile. He was the youngest prisoner still at Guantanamo, but younger boys were previously held there.
Canadian-born Khadr was taken to Afghanistan by his father, a senior al Qaeda member who apprenticed the boy to a group of bomb makers who opened fire when U.S. troops came to their compound. Khadr was captured in the firefight, during which he was blinded in one eye and shot twice in the back.
In a written statement, Toews said Canada received Khadr's application for transfer from the United States on April 13, 2012. He said U.S. officials assured Canada it would receive a videotape copy of an interview with Khadr, but it, along with other videotapes of interviews and unedited reports, was not sent until this month.
Former Canadian ambassador Gar Pardy, however, said Canada's Conservative government - which cultivates an image of being tough on crime - dragged out the transfer.
"I think the government was mainly very mean-spirited in how it handled the case," Pardy said to CTV News.
Toews said he continues to be concerned that Khadr "idealizes" his father and denies Ahmed Khadr's association with al Qaeda.
The U.S. Department of Defense confirmed that it transferred Khadr to Canada.
In the 2008 presidential election campaign, President Barack Obama promised to close the Guantanamo prison during his term, but that pledge has gone unfulfilled amid security concerns among Americans and opposition from Congress, which enacted laws making it more difficult to transfer prisoners from Guantanamo.
The transfer represents progress, but the Guantanamo prison should close immediately, said Suzanne Nossel, Amnesty International USA's executive director.
Canadian authorities should also investigate Khadr's allegations of torture while in the prison, she said.
"Canada now has the chance to right some of these wrongs."
Khadr's sentence will expire on Oct. 30, 2018.