Indonesian President Joko Widodo has defended the introduction of chemical castration for paedophiles, saying in an interview published Wednesday there can be "no compromise" when it comes to tackling sex crimes.

Widodo introduced a series of tough punishments for child sex offenders in May through an emergency decree, including chemical castration and the death penalty, following an outcry over the fatal gang-rape of a schoolgirl.

Parliament last week voted to put the new regulations permanently on the statute book, as had been widely expected.

In an interview with the BBC, Widodo defended introducing chemical castration, a decision that has sparked anger from human rights activists and the Indonesian Doctors Association, which has said its members will not perform the treatment.

"Our constitution respects human rights, but when it comes to sexual crimes there is no compromise," he said, adding that the government "will hand out the maximum penalty" for such crimes.

"In my opinion... chemical castration, if we enforce it consistently, will reduce sex crimes and wipe them out over time," he said.

Indonesia is among a small group of places worldwide which use the measure, including Poland and some states in the USA. In 2011 South Korea became the first Asian country to legalise the treatment.

Chemical castration involves using drugs to reduce libido and sex drive.

Widodo was spurred into action after the murder and gang-rape in April of a 14-year-old girl. She was set upon by a gang of drunken men and boys as she walked home from school on the western island of Sumatra.

The leader of the gang was sentenced to death last month after being found guilty of premeditated murder, a crime already punishable by death before the new laws were introduced. Other members of the gang have been jailed.