UN human rights investigators say that they have found evidence of arbitrary detention, torture and other human rights abuses in Angola.
A working group led by Algerian lawyer Leila Zerrougui spent 10 days interviewing more than 400 detainees.
In a statement released to the media, Ms Zerrougui says they saw detainees who "showed visible signs of torture".
Angola emerged from a 27-year civil war in 2002 and has been receiving UN help to reform its judicial system.
The statement from the UN's Office of the High Commissioner for Human Rights in Geneva says that despite Angola's efforts "the present institutional and legal framework governing the aspect of deprivation of liberty is still flawed".
The working group found evidence that torture and ill-treatment were used to extract confessions from suspects at two prisons the capital, Luanda.
The investigators also said there were credible allegations that civilians are held incommunicado at military facilities in the oil-rich province of Cabinda.
Cabindans say they are culturally and historically distinct
"They are never produced before a judge," said Ms Zerrougui.
"The right to access to a lawyer and a corresponding legal aid system as guaranteed by the (Angolan) constitution, exists only in theory".
The group were denied access to Cabinda military prison where the alleged "secret detentions" take place.
Last month, a pro-independence Cabindan civic group complained that some of its members were arbitrarily arrested ahead of a visit to the province by President Jose Eduardo dos Santos.
Mpalabanda had documented human rights violations by both government and Flec forces in Cabinda.
The organisation was unexpectedly shut down by court order shortly after the government signed a memorandum of understanding with Cabindan representatives in August 2006.
The deal was aimed at ending nearly three decades of sporadic uprisings by Cabindan nationalists seeking independence and a fair share of the offshore oil wealth for the province, but the details were not made public.