April 18, 2016, 12:31 am TWN
Duterte, who promises mass killings of suspected criminals if elected next month, appears in a video uploaded on YouTube making the joke about the female Australian missionary.
The missionary, 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 mayor at the time.
"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 bitch. 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 the preferred candidate in the run-up to the May 9 election, according to the latest opinion survey on April 3.
His rivals, women's groups and commentators on social media quickly denounced his remarks.
President Benigno Aquino's spokesman Herminio Coloma said the comments show "his lack of fitness for the presidency" and his "utter lack of respect for women."
"They got to her before me"
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.
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'."
Duterte refused to apologize for his remarks, insisting: "This is how men talk."
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.
Another candidate Senator Grace Poe, who is just behind Duterte in the surveys, called his comment "distasteful and unacceptable.
One Filipino remarked on Twitter: "I broke down after watching Duterte on Aussie rape. I can't fathom how his followers can laugh at it." Women's group Gabriela attacked Duterte's remarks, saying rape or any other form of sexual abuse was not a joke "nor something to be trivialized in a joke."
Many of his followers brushed off the controversy. "We won't apologize for he has done nothing wrong, it was a clear joke for God's sake," one Filipina supporter said on Twitter.