Philippine President Rodrigo Duterte gestures while speaking during a late night news conference - Reuters

Philippine President Rodrigo Duterte has declared himself in favour of same-sex marriage in an about turn that will put him on a collision course with the country's powerful Catholic Church.

Speaking at the weekend at a gathering of the LGBT community in his home city of Davao, southern Philippines, he vowed to protect their rights and invited them to nominate a representative to work in his government.

"I am for (same) sex marriage if that is the trend of modern times," he said. "If that will add to your happiness, I am for it."

Mr Duterte was quoted previously in the local media as opposing same-sex marriage, using the gender issue to attack liberal Western countries who allow it, especially those criticising his brutal war against drugs which has killed thousands of Filipino citizens.

Profile | Rodrigo Duterte

But according to the local Inquirer, Mr Duterte dramatically backtracked from earlier remarks in his latest speech, revealing that he had gay family members and joking that he once toyed with the idea of being bisexual.

"Why impose a morality that is no longer working and almost passe," he said, adding that "there will be no oppression" during his term in office and that his government would recognise the LGBT community's "importance in society".

His shift will put him at odds with the Catholic Church who have already strongly criticised his bloody crackdown on drugs. The country's powerful bishops earlier this year voiced concern about any moves to legalise same-sex unions.

While most Western countries have legalised same-sex marriage, with Australia being the latest to do so, the LGBT community still faces widespread discrimination across Asia. Only Vietnam and Taiwan have made progress towards marriage equality but have yet to enshrine the right to marry a member of the same sex in law.