Indonesia's president will soon sign a decree authorizing the use of chemical castration to punish pedophiles, the attorney general said, following a string of headline-grabbing child sex crimes.

Indonesia will join a small group of nations that allows such punishment, including Poland, Russia and Estonia, as well as some US states. In 2011, the Republic of Korea became the first Asian country to use chemical castration as a punishment.

"We are very concerned about child molestation abuse cases. This phenomenon has reached extraordinary levels," Attorney General H.M. Prasetyo told reporters after a cabinet meeting late on Tuesday.

"It has been agreed that there will be additional punishment in order to make people think a thousand times before doing this," he said.

President Joko Widodo was expected to soon issue a presidential decree approving the punishment after the Cabinet agreed to the measure late on Tuesday, Prasetyo said.

Chemical castration would involve injecting convicted pedophiles with a female hormone in the hope "his sexual desire will vanish", he said.