SREBRENICA, Bosnia-Hercegovina  - Bosnians on Wednesday buried 520 victims of the 1995 Srebrenica massacre, with the two alleged masterminds of the slaughter finally on trial for genocide.About 30,000 people gathered at a special memorial centre in Potocari, just outside Srebrenica, for the mass funeral on the 17th anniversary of the worst single atrocity on European soil since World War II.After speeches and the Muslim prayer for the dead, people began hoisting the simple coffins covered in green cloth to carry them to the freshly dug graves. Clouds of red dust rose over the vast cemetery as relatives covered the caskets with earth under the sweltering afternoon sun. Mujo Salihovic, 30, had come to bury his father and one of his brothers -- his other brother was already among the 5,137 victims already laid to rest there."I haven't told my mother that they will be buried today. She is sick and still believes they will return," he said tearfully. "If I tell her, it would kill her. I cannot lose her, she is all that I have left".It is the first anniversary being commemorated since the massacre's alleged architects, Bosnian Serb military commander Ratko Mladic and political leader Radovan Karadzic, went on trial before the UN war crimes court.In all, around 8,000 Muslim men and boys were slaughtered by Bosnian Serb troops in the 1992-95 war. Obama slammed moves to downplay the scale of the massacre in a clear swipe at Serbia's new President Tomislav Nikolic, who said last month that the killings in Srebrenica constituted "grave war crimes" but not genocide."The United States rejects efforts to distort the scope of this atrocity, rationalise the motivations behind it, blame the victims, and deny the indisputable fact that it was genocide," he said.Holocaust-survivor and US rabbi Arthur Schneier, who spoke at the commemoration, condemned the massacre and also the international silence in the face of grave injustice that allowed it to happen, drawing a comparison with events in Syria."Silence is not a solution; it merely encourages the perpetrators and ultimately it pays a heavy price in blood," he said. "It is a lesson that the world must learn again today as we witness the massacres being perpetrated by the regime in Syria against its own people. It is time again for humanity to say with one clear voice: these crimes must end," he urged.Many survivors and relatives in Srebrenica said Wednesday the trials at the International Criminal Tribunal for the former Yugoslavia (ICTY) in The Hague are too little, too late."It hurts me to watch broadcasts of the trials... it does not comfort me. (Karadzic and Mladic) plead not guilty, they say this was not genocide," Muniba Cakar, who buried her husband, said bitterly."It should be enough to come here and see the thousands of graves. If that is not proof, we should give up," the 63-year-old said, gesturing at the thousands of simple white headstones around her. The trial of Mladic, who commanded the attack on Srebrenica, resumed in The Hague this week with the first prosecution witnesses testifying, a little over a year since his arrest in Serbia after nearly 16 years on the run.Karadzic is due to start presenting his defence in October. His trial opened in 2009 after he evaded justice for 13 years. Both men have pleaded not guilty to genocide charges for masterminding the massacre and all other charges against them over the Bosnian war that left around 100,000 people dead.So far 38 former Bosnian Serb military or police officials have been convicted, including some for genocide, for their role in the Srebrenica killings, both by the ICTY and Bosnia's own war crimes court. In the past 17 years, the remains of 6,800 victims have been identified, but the search goes on as excavations of mass graves continue.