Manila: The Philippine military came under increased pressure Tuesday to rescue more than 20 foreign hostages after their captors beheaded a Canadian man, but troops face a dilemma in how to succeed without endangering the remaining captives.

Former Canadian mining executive abducted by the Abu Sayyaf last September was confirmed dead early Tuesday (Manila time) after his severed head was found in Jolo town, officials said.

The head of John Risdel, 68 was recovered by police at around 8:30pm inside a sack that was left by two men riding a motorcycle in Sulu’s capital, Jolo, officials said.

Earlier, the Abu Sayyaf warned in a video that they would execute Risdel and the three other captives--- Canadian Robert Hall, 50 as well as Norwegian resort manager Kjartan Sekkingstad, 56, and Hall’s Filipina partner Marites Flor, if the victim’s family do not pay ransom.

Risdel according to the firm that he used to head, TVI Resources Philippines, was “semi-retired,” at the time of his abduction last September 21, 2015.

The four were abducted by 11 armed men at the Holiday Oceanview Resort in Samal Island in Davao Oriental. They were later on taken by boat to Sulu, some 500 kilometres away.

Reacting to the news on the execution of one of their nationals by the militants, Canadian Prime Minister Justin Trudeau said he was “outraged” by the development.

“Canada condemns without reservation the brutality of the hostage-takers, and this unnecessary death. This was an act of cold-blooded murder and responsibility rests squarely with the terrorist group who took him hostage.

“The Government of Canada is committed to working with the Government of Philippines and international partners to pursue those responsible for this heinous act and bring them to justice,” he said.

Likewise, Trudeau expressed concern over the safety of the remaining Canadian hostage, Robert Hall, as well as Sekkingstad and Flor.

“The Government of Canada’s first priority is the safety and security of its citizens. The Government of Canada will not comment or release any information which may compromise ongoing efforts or endanger the safety of the remaining hostages.”

Hours before the execution on Monday, a joint police-military task group set in motion operations to rescue the four hostages.

President Benigno Aquino III issued instructions to acting Armed Forces Chief Lt Gen. Glorioso Miranda and national police Director General Ricardo Marquez “to conduct appropriate military and law enforcement operations to effect the rescue of the hostages.”

Some 400 Abu Sayyaf members and their supporters are estimated to be involved directly and indirectly in the abduction.

Just last Friday, soldiers Major Filemon Tan, spokesperson of the Western Mindanao Command regional commander, said an encounter occurred at 11pm in n the town of Patikul in Sulu where seven soldiers were wounded.

The clash was said to have been connected with efforts to rescue the hostages.

Rocky Dimaculangan, a former employee of TVI Resources and a friend of Risdel, remembers the Canadian mining executive fondly.

“He just wanted to sail his boat. John loved to talk a lot. About his boat and the many shores he had reached sailing alone or with his family. His two daughters and their work,” he said.

“His belief that responsible mining can make a big difference for our nation. His advocacy that transparency and an open-door policy will make people understand that responsible mining is possible and is actually happening. His love for the Philippines and its people; his concern for its indigenous people,” he said.

After working for several years in the Philippines as a mining executive, Risdel had retired on semi-retirement in Mindoro.

Contacted earlier by Gulf Newsr, TVI Resources said Ridsdel had been suffering from a number of illnesses. “He was seeking medical treatment for tuberculosis, pneumonia and a knee injury.”

“The pressure on the armed forces is really immense,” said Julkipli Wadi, who has conducted extensive studies on the Muslim secessionist conflict in the south.

The military has to contend with escalating territorial disputes in the South China Sea while dealing with Muslim and Marxist rebellions that have endured through several presidencies, fuelled by the poverty, neglect and desperation that have not been tamed by political leaders, Wadi said.

A large-scale offensive could displace many villagers and draw attention to the long-standing security and social issues in the vote-rich south, homeland of minority Muslims in the largely Roman Catholic nation.

— with inputs from agencies