MANILA, Philippines - The Philippines' presumptive president-elect said Thursday he apologized to Canadian Prime Minister Justin Trudeau over the beheading by Muslim militants of a Canadian hostage in the southern province of Sulu.

Mayor Rodrigo Duterte of southern Davao city told reporters he apologized for last month's beheading of hostage John Ridsdel when Trudeau called Tuesday to congratulate him for his election victory.

"I said 'Mr. Prime Minister, please accept my apologies for the incident,"' Duterte told reporters in Davao. "We will try our very best and see to it that nothing of this sort will happen again, and you can rest assured that when the time comes, we will be able to apprehend the criminals and exact justice."

Duterte, who won the May 9 presidential election on a wide margin based on an unofficial tally, is due to be inaugurated president on June 30, the end of outgoing leader Benigno Aquino III's six-year term.

The militants beheaded John Ridsdel on April 25 in Sulu, an impoverished province in the south after they failed to get a ransom of 300 million pesos ($6.3 million).

Trudeau earlier condemned the killing but vowed not to give in to the kidnappers' ransom demands. Following the beheading, the Philippine military launched an offensive that security officials believe have killed more than a dozen gunmen so far.

Muslim militants have threatened to kill three more hostages in their jungle base in the southern Philippines weeks after beheading Ridsdel. The hostages include another Canadian, a Norwegian and a Filipino woman.

Duterte said he and Trudeau also discussed human rights, and he said he told Trudeau: "Universal Declaration of Human rights, fine, I said 'I'm following it, but Mr. Prime Minister, with few exceptions."'

Duterte has been criticized for his human rights record in Davao, where he was mayor for 22 years. Hundreds have been killed in that port city on an anti-crime purge some believed he secretary run. On the presidential campaign trail, Duterte repeatedly vowed to kill drug criminals.

Investigators have said they have found no hard evidence of a direct role by Duterte in the vigilante-style killings, saying not one witness has come forward to testify against him.