The internal workings of a vast chain of Chinese internment camps used to detain at least a million people from the nation’s Muslim minorities are laid out in leaked Communist Party documents published on Sunday.

The China Cables, a cache of classified government papers, appear to provide the first official glimpse into the structure, daily life and ideological framework behind centres in north-western Xinjiang region that have provoked international condemnation.

Obtained by the International Consortium of Investigative Journalists (ICIJ) and shared with the Guardian, the BBC and 15 other media partners, the documents have been independently assessed by experts who have concluded they are authentic. China said they had been “fabricated”.

However, the documents are consistent with mounting evidence that the country runs detention camps that are secret, involuntary and used for ideological “education transformation”.

When reports surfaced of mass internments without trial, authorities in Beijing initially denied the existence of the detention centres, whose inmates are mostly Uighurs and other ethnic minorities.

After satellite photos and a flood of testimony from former detainees and relatives became impossible to ignore, the party insisted they were for voluntary “vocational training”.

The cables provide apparent confirmation from within China’s bureaucracy that the camps were envisaged from the start as brainwashing detention centres, to be constructed on a massive scale, with inmates confined by multiple layers of security.

Signed in the name of Zhu Hailun, the top security official and deputy Communist party chief in Xinjiang, it sets out how the centres were designed to expose detainees to a period of enforced indoctrination.

The document states:

• Camps must adhere to a strict system of total physical and mental control, with multiple layers of locks on dormitories, corridors, floors and buildings. Fences should be put around each building, and walls around the compound. A dedicated police station must be at the front gate, all monitored by security guards in watchtowers.

• Inmates could be held indefinitely – but must serve at least a year in the camps before they can even be considered for “completion”, or release.

• The camps are to be run on a points system. Inmates earn credits for “ideological transformation”, “compliance with discipline” and “study and training”.

• Even after completing their “education transformation” inmates are not allowed to go free. They move into another tier of camps, where they face a further three- to six-months’ internment for “labour skills training”.

• Weekly phone calls and a monthly video call with relatives are their only contact with the outside world, and they can be suspended as punishment.

• “Preventing escape” is a top priority. The order demands round-the-clock video surveillance “with no blind spots” to monitor every moment of an inmates’ day. Control of every aspect of their lives is so comprehensive that they have to be assigned a specific place not only in dormitories and classrooms, but even in the lunchtime queue.