Bosnia is commemorating the 20th anniversary of the massacre of 8000 Muslim men and boys in the UN-protected enclave of Srebrenica, with debate continuing to rage over its description as genocide.
The remains of 136 newly identified victims will be laid to rest along with more than 6000 others already buried at a memorial centre just outside the eastern Bosnian town.
Thousands of Muslim men and boys were slaughtered by Bosnian Serb forces after they captured Srebrenica in July 1995 near the end of Bosnia's inter-ethnic war, in the worst atrocity on European soil since World War II.
About 50,000 people, as well as dignitaries from across Bosnia and abroad, are expected to be present at Saturday's ceremony marking two decades since the massacre.
A day of mourning will be observed throughout the Balkan country.
International officials due to attend include European Union foreign policy chief Federica Mogherini and Bill Clinton - the US president at the time, whose administration brokered the Dayton peace deal that ended Bosnia's 1992-95 war only a few months after the Srebrenica slaughter.
Clinton also attended the massacre's 10th anniversary.
Serbia, which backed Bosnian Serbs during and after the war that claimed about 100,000 lives, will be represented by its Prime Minister Aleksandar Vucic, a former ultranationalist-turned-pro-European.
Serbian and Bosnian Serb politicians have long denied the scale of the killing in Srebrenica, although two international tribunals have described the bloodshed as genocide.
But all of Serbia's leaders, including Vucic, have persistently refused to acknowledge it that way.