SYDNEY, Australia — The number of Indigenous Australian juveniles in detention, on bail or on parole is increasing, even as the total number of children accused of crimes in Australia is decreasing, a government agency said Friday.

Indigenous Australians are disproportionately represented in the youth justice system and are 18 times more likely than their nonnative counterparts to be under “justice supervision,” according to a report by the Australian Institute of Health and Welfare.

Of the 5,359 minors aged 10 to 17 under supervision on an average day last year, about half of them came from the country’s Aboriginal and Torres Strait Islander communities, according to the report. But children from those same communities made up only 5 percent of the country’s population for the same age group.

“We have been tracking the Indigenous and non-Indigenous kids in justice supervision, and the rate for Indigenous kids is falling slower than non-Indigenous kids,” said David Braddock, the institute’s spokesman.