KANANASKIS, Alta. -- Prime Minister Justin Trudeau condemned Monday the "cold-blooded murder" of a Canadian beheaded by terrorists in the Philippines after being held hostage for seven months.

Trudeau confirmed the victim was 68-year-old John Ridsdel of Calgary.

Ridsdel was one of four tourists -- including Canadian Robert Hall, a Norwegian man and a Filipino woman -- who were kidnapped last Sept. 21 by Abu Sayyaf militants from a marina on southern Samal Island.

The militants had threatened to kill one of the three male hostages if a large ransom was not paid by 3 p.m. Monday local time -- 3 a.m. ET.

Trudeau said he was "outraged" by the news that a plastic bag containing Ridsdel's decapitated head was dumped in a street Monday night by two men on a motorcycle in Jolo, a town in Sulu province.

"Canada condemns without reservation the brutality of the hostage takers and this unnecessary death," Trudeau said in a hastily assembled appearance before the media in the midst of a cabinet retreat.

"This was an act of cold-blooded murder and responsibility rests squarely with the terrorist group who took him hostage."

Trudeau said the Canadian government is committed to working with the Philippine government and international partners to "pursue those responsible for this heinous act and bring them to justice."

On behalf of all Canadians, he also expressed his "deepest condolences" to Ridsdel's family and friends.

"They have endured a terrible ordeal and this is a devastating moment for all of them."

Saying that the safety of Canadian citizens is the first priority of the government, Trudeau said the government will not comment or release any information that might "compromise ongoing efforts or endanger the safety of the remaining hostages."

He did not answer any questions, including whether the government had paid a ransom for Ridsdel or Hall. However, an official said it is long-standing government policy to not pay ransom demands.

In militant videos posted online, Ridsdel and fellow Canadian Robert Hall, Norwegian Kjartan Sekkingstad and Filipino Marites Flor were shown sitting in a clearing with heavily armed militants standing behind them. In some of the videos, a militant positioned a long knife on Ridsdel's neck. Two black flags hung in the backdrop of lush foliage.

The abductions highlighted the long-running security problems hounding the southern Philippines, a resource-rich region that suffers from poverty, lawlessness and decades-long Muslim and communist insurgencies.

Abu Sayyaf emerged in the early 1990s as an offshoot of a separatist rebellion by minority Muslims in the predominantly Roman Catholic nation's south.

The group -- which Canada and other western countries consider a terrorist organization -- has relied on extortion and huge ransoms earned from kidnappings of mostly Western tourists and missionaries to survive for more than two decades.

With files from The Associated Press.