The "Prisons within Prisons" report was based on interviews with 18 prisoners of conscience who had collectively spent more than 77 years in prison for activism, questioning social injustice or simply for their ethnicity or religious beliefs.

Interviewees recounted being beaten until they urinated blood, given electric shocks and confined in isolation without access to family members or lawyers.

"On one occasion, pens were placed between his fingers and his hands were twisted around, causing excruciating pain," the report reads.

The report accuses Vietnamese officials of using prisoners known as "antennae" who would work with the authorities, take part in the torture and continue interrogations inside prison cells, in exchange for favorable treatment.

In the most extreme case, a Hoa Hoa Buddhist called Mai Thi Dung was forced to share cramped cells with a series of different women who would question her about her activism at night, after she had endured up to 10 hours of interrogation by authorities. She was locked in a tiny room "with no open windows or ventilation shafts resulting in such bad ventilation that it was difficult to breathe."

A poor track record

Vietnam, a one-party state, is regularly denounced by rights groups and Western governments for its intolerance of political dissent and systematic violations of freedom of religion.

In June a group of six Vietnamese civil society organizations called for development aid to Vietnam from foreign governments and banks to be tied to improvements in the one-party communist state's rights record.

The New York-based Human Rights Watch (HRW) reported in February that Vietnam's rights situation was “critical.”

"Rights activists and dissident bloggers face constant harassment and intimidation, including physical assault and imprisonment. Farmers have lost land to development projects without adequate compensation, and there is an absence of independent unions for workers," HRW said.

About 150 political prisoners are currently imprisoned by the regime, the group added.

Agence France Presse - July 12, 2016