The US-based group Human Rights Watch says it has heard dozens of credible accounts of torture and beatings by police in East Timor.
In a report issued on Wednesday, the group calls on the East Timorese government to take urgent action to prevent such abuse becoming routine.
The former Portuguese colony was ruled by Indonesia for nearly 24 years before a UN-sponsored referendum in 1999.
East Timorese police chief Paulo Martins denied the torture charges.
“We treat our prisoners finely and in line with procedures,” the Associated Press news agency quotes him as saying.
He urged Human Rights Watch to send him proof of abuse.