READ THE LATEST: Family 'devastated' by loss of Canadian killed by kidnappers in Philippines

A former Calgarian who has been held hostage in the Philippines for nearly six months with a second Canadian and two others is pleading for Prime Minister Justin Trudeau to do what's needed in order to secure their release.

"To the Canadian prime minister and to the Canadian people in the world, please, do as needed to meet their demands within one month or they will kill me," John Ridsdel said in a video released Mar. 10 on a Facebook page linked to Philippine Islamists.

"They will execute us."

Ridsdel — a former mining company executive living in semi-retirement — was abducted along with fellow Canadian Robert Hall, a Norwegian and a Filipino woman on Sept. 19 from an upscale beach resort on an south Philippine island.

In the video, the three men are shown handcuffed on the ground. They are thin and shirtless.

The video was later removed from the Facebook site.

'They are really losing a lot of weight'

Freelance journalist Dean Bernardo, who has seen the video and recently visited the area where the group was abducted, told the Calgary Eyeopener that the hostages are not in great condition.

"They are really losing a lot of weight. They don't seem to be well treated," he said.

Bernardo said their abductors are with the al-Qaeda-linked Abu Sayyaf militants who have been active for years in the Mindanao region and are known for kidnapping for ransom.

A still image taken from a video released by Abu Sayyaf militant kidnappers shows Canadians Robert Hall (left) and John Ridsdel (centre). The third male hostage is Norwegian Kjartan Sekkingstad. (Reuters/YouTube )

"These are isolated islands," said Bernardo.

"You know there is no sufficient food or water in those areas."

Ridsdel is the former chief operating officer of mining company TVI Resource Development Philippines Inc., a subsidiary of the Calgary-based TVI Pacific, where he is still a consultant. Decades earlier, he had worked as a journalist in the 1970s, including with the CBC in Calgary.

'We will do something terrible,' captors warn

The latest video does not specify how much the ransom is, but one of the kidnappers did issue a one-month ultimatum.

"We will do something terrible against these captives," the masked spokesman says in the video.

The hostages were taken on Sept. 19 from the Oceanview resort on Samal island, near Davao City, the largest city on Mindanao island in the southern Philippines. (Google)

In a November video released by the Abu Sayyaf militants, Ridsdel said the militants were demanding one billion pesos, or $28 million Cdn, for each of them.

Bernardo expects that price will go down considerably as the April deadline approaches.

"They're hoping somebody will respond. Even if it's a small amount of money."

The Philippine Army is pursuing the kidnappers and say they are closing in.

"We're getting closer to them, hence, they needed to expedite the demand for ransom in order for them to escape from the hands of the law, which is closely catching up," military spokesperson Restituto Padilla told Reuters.

However, Padilla said Philippine authorities will not negotiate with the kidnappers.

The Canadian government told CBC News it is aware of the video that was released this week, but "would not comment or release any information which may compromise ongoing efforts or endanger the safety of Canadian citizens."

With files from the Calgary Eyeopener and Reuters