The Prove They Are Alive! rights campaign has called on the international community to pressure Turkmen authorities to curtail the practice of enforced disappearances in the Central Asian nation's prison system.

The group said in a statement that "hundreds of people have become victims of enforced disappearance" in Turkmenistan and called the situation "a gross violation of Turkmenistan’s national legislation and of its international obligations" and "a human rights crime."

Rights groups say that, in many cases, prisoners who have disappeared in the custody of Turkmen authorities have been convicted on politically motivated charges and have been perceived as a potential threat to the authorities in Ashgabat.

The Prove They Are Alive! campaign says it has documented over 120 cases of disappearances in Turkmenistan's prisons.

"Inhuman conditions in the prisons where the disappeared are held correspond to torture. At least 27 individuals from this list have died in prison; the real number of those who have disappeared and died in isolation during these years is likely much higher," the statement says, adding that "this is an ongoing crime."

According to the campaign, there are men held incommunicado in unknown prisons across Turkmenistan, whose terms have already expired or will expire in the next two years.

The statement says that the campaign sent a letter to Turkmen President Gurbanguly Berdymukhammedov regarding the disappeared men in December.

"The campaign hopes that President Berdymukhammedov will take positive steps to resolve this critical situation in the nearest future," the statement says.

"The international community must continue to attentively follow this situation and demand real action from the Turkmen leadership to stop enforced disappearances. Any international cooperation with the government of Turkmenistan must be contingent upon positively resolving the problems of the disappeared in Turkmenistan’s prisons," the statement concludes.

Turkmenistan -- where every facet of society is tightly controlled by the president -- is at the bottom of international ratings that measure freedom and democracy.

In Freedom House's index on basic freedoms, Turkmenistan is rated worse than North Korea and only ahead of Syria.