The idea that Ukrainian prisoners in occupied Donbas are being exploited for cheap labor is disturbing. Some captive inmates are physically forced to carry out unpaid, often back-breaking manual labor, despite being granted amnesty by President Petro Poroshenko.

Human rights activists have published fresh evidence suggesting hundreds of convicts serving time in occupied Luhansk region are in this situation. In a recent report by the 'Eastern Human Rights Group', researchers documented cases of prisoners working more than 12 hours a day and being threatened with beatings, torture, and even death. Cases of abuse were reported in at least 10 detention centers in the occupied Luhansk region, activists said.

Pavel Lysianskiy is one of the several authors of the report. His organization says it spoke to over 70 people including relatives of prisoners serving time in those detention centers, prison service workers, and even the prisoners themselves. The majority interviewed chose to remain anonymous, fearing retribution.

"This is exactly what 'slave labor' looks like in the 21st century", Mr. Lysianskiy said, during an interview with Hromadske International reporter Tamara Rozouvan.

The findings have not gone unnoticed. On October 13, members of the Parliamentary Assembly of the Council of Europe (PACE) deplored the 'legal and humanitarian situation of ordinary detainees' who are subject to 'various forms of inhuman and degrading treatment'. Publically condemning the Kremlin-backed de-facto leadership in Luhansk region is one thing. Drafting and implementing an effective strategy to deal with the prisoners' plight is another.

The Russian-backed militants may be 'reinventing' slavery, but it might be the Ukrainian government who will be paying the compensation. Over 1,000 prisoners jailed for non-violent crimes were supposed to be released under an amnesty issued by Mr. Poroshenko in 2014. At the time, the state penitentiary service dismissed any negotiations with 'a terrorist organization' and failed to secure their release. Fast forward to October 2016 and the Russian-backed separatist forces still refuse to free the prisoners.

"The prisoners who are being held in illegal captivity will return to Ukraine and they will take the government to court ... It was the Ukrainian government who placed them there," Mr. Lysianskiy explained, "and it's their (the Ukrainian government's) responsibility to take care of their citizens and secure their release."

Prison labor has always been a lucrative business in Russia and its former Soviet satellite states, according to analysts at the Kharkiv Institute of Social Research. The report claims, in 2012, the Ukrainian government profited $ 100,000 a month from prison labor. This compares to latest estimates which suggest prisons in the occupied Luhansk region are generating between $ 300,000- $ 500,000 a month for the Russian-backed separatist forces, according to figures calculated by the 'Eastern Human Rights Group'. Verifying such data is almost impossible in the occupied territory.

Prisoners have spoken of producing a range of goods including bricks, barbed wire, board games, scrubs, medical lab coats and even wooden souvenirs. Websites affiliated with the so-called 'Luhansk People's Republic' openly advertise these products. Potential buyers could even be Ukrainian companies. It's unsettling to imagine some souvenirs sold in Kyiv could have been manufactured in one of these Soviet-style prisons by inmates physically forced to make them.

Alexander Efreshin is one prisoner who contacted the BBC in an attempt to the generate awareness of the conditions inside one detention center. His sister Irina told Hromadske that this was a desperate attempt, made by an even more desperate man.

"He told me that he will not be able to last in these conditions for three more years."

At the age of 24, Alexander was sentenced to eight and a half years in prison for arson and robbery. His friends and family expected his release in April 2015. It never came. Irina says the occupying Russian-backed separatist forces plan to keep him incarcerated until 2019.

"They use (the prisoners) as slaves. They do not pay them anything. They do not feed them properly and they make them work. When they die, nobody will care; after all, they're just prisoners, "

Irina says the government is ignoring many of the prisoners' relatives, adding some even feel seeking help from the state has become more difficult since the penitentiary service was dismantled this year as part of the reform process. Now, they need to appeal to the Justice Ministry.

Meanwhile, the Ukrainian Ombudsman Valeria Lutkovska is making progress in the occupied Donetsk region. Her team has secured the release of more than 100 people in the last few months. But in occupied Luhansk region, the so-called leaders are more unpredictable and nearly impossible to negotiate. That's according to Mykhailo Chaplyga, Ms. Lutkovska's representative.

Alexander vows to fight for his release until 'the end'. He plans to go to court to seek compensation for the 'rehabilitation' he will need - if or when he's finally released. Irina told Hromadske that Alexander is no longer the only one standing up for his rights and his own life. A number of prisoners' relatives have approached her, seeking to come forward with their own personal stories.

A former head Ukraine's state prison service Serhiy Starenkiy says the prisoners who have served their time but are still held captive will have 'a good chance' of a European court ruling in their favor and getting compensation from their government.

While lawyers mull over such cases, Ukrainian prisoners in occupied Luhansk such as Alexander are still being held hostage. Irina hopes the media coverage generate by his plight will help to secure his release.