From international observers and journalists to pro-Ukrainian activists, priests and ordinary citizens, cases of arbitrary detention and abductions are on the rise in the areas of eastern Ukraine controlled by pro-Russian rebels.
"Kidnappings began from the very beginning of the insurgency and today we estimate the number of those being detained illegally at 200," Maria Oliynik, an activist with Ukrainian rights watchdog Prosvita, told AFP.
Those held hostage are usually kept in basements and safe houses guarded by gunmen from the rebel "authorities" of the self-proclaimed republics of Donetsk and Lugansk in eastern Ukraine -- and the United Nations says they can face beatings, torture and even execution.
But after almost two months of bloodshed in the region the situation is chaotic and with rebels splintering into different groups it is sometimes difficult to tell which faction is actually holding the detainees.
For close to a fortnight now two groups of observers from the Organisation for Security and Cooperation in Europe (OSCE) -- totalling eight international monitors and a Ukrainian interpreter -- have been held captive and incommunicado after separatists picked them up, three days apart, in late May.
These latest abductions come after seven OSCE observers sent to Ukraine by the Vienna-based organisation to pacify the region and foster dialogue were held for eight days by pro-Russian rebels in their stronghold city of Slavyansk and released in early May.
But while some rebel leaders in Slavyansk have reportedly claimed the observers are in their custody others say that they have no idea where they are.
"We are searching for these observers, but we are not able to control the whole territory (of the Donetsk region)," Aleksandr Borodai, the "prime minister" of the "People's Republic of Donetsk" and in theory the senior rebel official in the region, told reporters on Saturday.
- Killings, torture -
Beyond the headline-grabbing seizure of international observers, the latest reports from the United Nations, OSCE and Human Rights Watch confirm that the scale of abductions is growing.
A recent UN report cited "numerous instances of killings, torture, beatings, kidnappings and intimidation mostly perpetrated by well-organised and well-armed anti-government groups in the country's east".
The report highlights "the alarming increase in kidnapping and illegal detention of journalists, activists, local politicians (and) NGO representatives".
"Although some people were ultimately released, the remains of many others were thrown into rivers and other places," the document from May 16 reads.
- 'Prisoners of war' -
The rebels though deny the allegations of brutality and say the people being held are legitimate targets.
"They are mostly people who engaged in hostile activities, stuck up subversive leaflets and campaigned against the People's Republic of Donetsk," Leonid Baranov, the national security council member in charge of the "commission for the prisoners of war", told AFP.
"A decree was issued by the government to arrest those who engage in activities hostile to the People's Republic of Donetsk," he said.
Claiming that he was not aware of the total number of the "prisoners of war" being held in Donetsk, Baranov said a tentative estimate would be "some 15" people. He rejected as "lies" the testimonies of former prisoners about systematic beatings while in captivity.
International organisations report that those being held come from a wide range of backgrounds: miners union leader Oleksandr Vovk, Polish Catholic priest Father Pawel Witek, Protestant pastor Sergiy Kosiak, local officials from Ukrainian political parties, such as Yaroslav Malachuk and Artem Popyk, and journalists accused of spying.
Sometimes the pretext for detention can be very flimsy indeed, says human rights activist Oliynik.
"It can suffice that your ID card indicates an address in Kiev or in western Ukraine to become a suspect and be arrested. This was the case of the student from Kiev, Igor Khotria, who was arrested when he arrived to visit his family that lives near Donetsk," she said.
But there may be a deeper reason for the detentions, with separatists using those held as bargaining chips in negotiations over prisoner swaps with Kiev for rebel supporters they claim are being held illegally by the central government.
The separatist leader Aleksandr Borodai said Saturday that a prisoners swap was being negotiated with the assistance of the OSCE and UN representatives in Donetsk.
"We are in talks to achieve the release of the hostages. Insurgents now hold more than 200 people, citizens of different countries," Kiev-appointed governor of the Donetsk region Sergiy Taruta confirmed.