Indonesia has a "culture of impunity" in the face of ill-treatment and torture, a senior UN official has said.
The police are rarely punished for the abuse, Mr Nowak says
Manfred Nowak, special rapporteur on torture, has spent two weeks inspecting the country's prisons and police and military detention centres.
Mr Nowak said he found evidence of detainees being electrocuted, suffering systematic beatings and even being shot in the legs at close range.
He called on the government to make torture a separate crime under the law.
The BBC's Lucy Williamson, in Jakarta, says Indonesia has regularly come under scrutiny for its human rights record. Mr Nowak's visit is the third by a UN human rights monitor this year.
He conceded that treatment of detainees had improved since authoritarian dictator Suharto's regime came to an end in 1998.
But the envoy said abuse had continued, and the police appeared to be the main culprits.
Mr Nowak toured several regions of the country
"The problem of police abuse appears to be sufficiently widespread as to warrant immediate attention," he said.
The level of abuse varied widely between institutions, depending on the personal behaviour of those in charge, he said.
In some places there were no reported cases of abuse, in others he said torture was systematic, with detainees regularly suffering beatings.
"In all the meetings with government officials nobody could cite one case in which a police officer was ever found guilty and sentenced by a criminal court for ill-treatment or other abuse of a detainee," he said.
He called on the Indonesian government to strengthen the legal safeguards against torture.
He said there should be a separate offence of torture, a reduction in the time people spend in police custody and an independent complaints system.
Mr Nowak, who will deliver a full report to the UN Human Rights Council, visited institutions in Jakarta, Papua, South Sulawesi, Bali and Yogyakarta.