Indonesia's constitutional court is considering whether to make gay sex a crime after accepting a judicial review petition from Islamic activists.

A group calling itself the Family Love Alliance says an existing law that criminalizes sex between adults and minors of the same gender, and which mandates prison sentences of up to 15 years, should be amended to also apply to sexual acts between adults of the same gender.

Rita Hendrawaty, chairwoman of the group, said Wednesday it was not trying to criminalize lesbian, gay, bisexual and transgender people.

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"The real reason is so that we have much clearer norms," she said.

"We are not intending to criminalize those who have a deviant sexual orientation. That is not the point. They can be free to live but not show their lifestyle."

Indonesia's image for tolerance and moderation has been tested this year by a campaign of denigration against LGBT people involving conservative politicians, mainstream Muslim groups, professional associations and media organizations.

Homosexuality is not illegal in Indonesia, the world's most populous Muslim nation, but LGBT people can face stigma and discrimination. Criminalizing sexual activity between consenting adults would be a major backward step for human rights in the country.

Experts presented by the anti-LGBT group at a hearing on Tuesday testified that homosexuality was inherently immoral and went against Indonesia's state ideology.

Later this month, groups and individuals opposed to criminalizing gay sex will testify.

The Family Love Alliance also wants the nine-judge court to expand adultery laws to include unmarried people and for the definition of rape to be gender neutral. Currently the law defines rape as an act by a man against a woman.