Leading Philippine presidential candidate Rodrigo Duterte has refused to apologise after a video surfaced of him apparently joking about a murdered Australian rape victim.

Duterte, whose campaign promises a ruthless war on crime, refused to apologise for his remarks, insisting: "This is how men talk."

He was condemned after a video surfaced of him apparently joking about murdered Australian rape victim Jacqueline Hamill appeared on YouTube.

The woman, who was ministering in a prison in Davao in the southern Philippines, was raped and killed during a riot by inmates in 1989.

Duterte was the city's mayor at the time.

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Rodrigo Duterte refuses to apologise for the comments. Photo: AFP

"They raped all of the women... There was this Australian lay minister... when they took them out... I saw her face and I thought, 'Son of a b*****. what a pity... they raped her, they all lined up. I was mad she was raped but she was so beautiful. I thought, the mayor should have been first," Duterte is shown telling a crowd of laughing supporters at a campaign rally.

Duterte, who boasts of the extra-judicial killings of suspects by vigilantes during his time in Davao, is leading in the run-up to the May 9 election, according to the latest opinion survey on April 3.

In a response also uploaded on YouTube, Duterte insisted he had just been recounting the events of 1989 and was not making a joke about them.

"It was not a joke. I said it in a narrative," he said.

"I was very angry when I spoke. I said 'Sons of whores, she is as pretty as an American movie star. They got to her before me. So kill them all'."

His rivals, women's groups and commentators on social media quickly denounced his remarks but Duterte denied any levity.

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Jaqueline Hamill. Photo: Supplied

President Benigno Aquino's spokesman Herminio Coloma said the comments show "lack of fitness for the presidency" and his "utter lack of respect for women".

Aquino, who under the constitution cannot seek a second term, is supporting another candidate, his former interior secretary Mar Roxas who trails Duterte in opinion surveys.

Rival presidential candidate Vice President Jejomar Binay called Duterte's remarks "simply revolting".

"You are a crazy maniac who doesn't respect women and doesn't deserve to be president," Binay told Duterte in a statement.

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