Made Arya Kencana, Denpasar – Measures to protect children against sexual exploitation remain weak, Women's Empowerment and Child Protection Minister Linda Sari Gumelar said on Friday.

"We are still weak in documenting cases of child prostitution. The cases [documented] are just the tip of the iceberg," she said at a regional seminar on child sexual exploitation in Kuta, Bali.

The minister did not disclose how many cases of child prostitution her ministry or other agencies had recorded.

However, data from End Child Prostitution, Child Pornography and the Trafficking of Children (Ecpat) show up to 70,000 children in Indonesia may have fallen victim to sexual exploitation. "Poverty and a low level of education have forced a great number of children to be sexually exploited," said Ahmad Sofian, Ecpat's Indonesian coordinator.

The group says the majority of victims are from West, Central and East Java, West Kalimantan and North Sumatra. In many cases, the children are promised work as domestic workers but end up in prostitution dens.

More than 3,900 children here have fallen victim to human trafficking in the first half of the year, according to the International Organization for Migration. The country tops the UN body's list of child trafficking cases.