During the 1998 – 1999 war in Kosovo, more than 3,000 ethnic Albanians were victims of "enforced disappearances by Serbian police, paramilitary and military forces."
Similarly, "an estimated 800 Serbs, Roma and members of other minority groups were abducted, reportedly by members of the Kosova Liberation Army (KLA), the majority after the international armed conflict ended in June 1999, under the eyes of the NATO-led peacekeeping Kosovo force," Amnesty International said in a report published on Monday (8 June).
"A decade after the end of the war, around 1,900 families across Kosovo and Serbia still have no details about the fate or whereabouts of their missing relatives, said Amnesty's Balkans expert Sian Jones.
To date, little has been done for these cases to be resolved, due to a lack of at the same time means and political will in both Kosovo and Serbia.
The EU has a double role to play, Ms Jones told EUobserver on Tuesday.
It should increase political pressure on both Serbia and Kosovo to resolve these cases.
In Kosovo at the moment, "a fair number of the KLA who allegedly committed war crimes" are actually in the government and "a climate of fear" reigns among Kosovars, who risk being killed if they come forward and provide evidence against members of the KLA.
"The EU can give it a lead, really. Say ‘if you want to be a country, take a more responsible attitude," she said.
Additionally, the bloc's recently created rule of law mission in Kosovo, EULEX, should set up a good witness protection programme. For their part, member states could offer to provide witness protection to people ready to testify against alleged war criminals, she pointed out.
"People need to be taken out of the country and protected probably for the rest of their lives, to be honest. If each country could take one person and their family then that would actually make a significant contribution to justice," the researcher said.
In Serbia too the EU should do more, she stressed, especially in terms of providing assistance and financial support.
"There should be support from the EU in Serbia… They need more courts, they need more judges and investigators, and they need an independent set of investigators by the police… We would like more resource put into Serbia," she said.
The EU should also not focus exclusively on the arrest of the two remaining war crimes suspects, Ratko Mladic and Goran Hadzic, when the people who were working with them during the war and executing their orders are still "at large, they are in government, they are around actively influencing what is going on in society."
"Some of the member states are a little bit preoccupied with that [arresting the two fugitives]. And okay, it's important, but it's not the only thing," Ms Jones said.
In its report, Amnesty also criticised UNMIK, the UN mission governing Kosovo between 1999 and its declaration of independence last year.
It said UNMIK suffered from a lack of accountability as well as a lack of impartiality, and accused it of "interference in the course of justice."
"They sacrificed human rights by more or less refusing to undertake a number of prosecutions against ethnic Albanians" in the name of keeping political stability, Ms Jones said.
The EU has "a completely different role," she underlined, and reiterated calls on the EULEX mission to use its "potential of resolving the [pending] cases."
Amnesty International has included its concerns and recommendations in a communication it submitted to the European Commission on Tuesday, in light with the EU executive's preparation of its annual reports on the western Balkan countries' progress towards the EU.