Tens of thousands of people have attended ceremonies marking the 10th anniversary of the massacre of Bosnian Muslims in Srebrenica.
Grieving relatives buried more than 600 newly identified dead, after prayers and words of support from international and local officials.
About 8,000 men and boys were killed by Bosnian Serb forces in 1995 in Europe's worst atrocity since World War II.
Serbian officials led by President Tadic paid respects for the first time.
Muslim prayers echoed through the valley of the memorial site at Potocari, the site of the slaughter, as women in white headscarves wept beside the remains of their loved ones.
The green coffins were then passed from hand to hand through the crowd to the freshly dug grave sites, as announcers called out one by one the names of the 610 dead.
Each family buried its own dead, by hand or using shovels and buckets.
Serbia's parliament observed a minute silence for all victims of atrocities in and around Srebrenica, and also of last week's London bomb attacks.
1: Bosnian Serb forces advance on Srebrenica. Thousands of Bosnian Muslims flee
2: More than 20,000 people flee to Potocari, seeking help from Dutch peacekeepers. But Serb forces enter the camp, killing the men and boys
3: Killing sites include a football field in Nova Kasaba
4: Thousands of males are killed trying to reach the Muslim-controlled city of Tuzla
But it failed to make specific reference to the Srebrenica massacre, and was boycotted by the ultra-nationalist Serbian Radical Party.
Earlier, UK Foreign Secretary Jack Straw apologised on behalf of the international community for failing to stop the atrocity.
"For it is to the shame of the international community that this evil took place under our noses and we did nothing like enough. I bitterly regret this and I am deeply sorry for it," he said.
He said that it was "sickening" that former Bosnian Serb leader Radovan Karadzic and his army commander Gen Ratko Mladic, who are accused of the slaughter, had not yet been brought to justice.
UN Secretary General Kofi Annan said Srebrenica would haunt the organisation forever in a statement read out at the ceremony.
EU foreign policy chief Javier Solana and former US Balkans envoy Richard Holbrooke also described it as a collective failure.
Meanwhile the Hague tribunal's chief prosecutor, Carla del Ponte, boycotted the occasion to protest against the failure to arrest Mr Karadzic and Mr Mladic.
In Serbia, many still believe the mass killings never took place. But a new video showing the execution of Muslim civilians sparked national soul-searching among Serbs last month.
Convicted, cases completed - 3 including former Bosnian Serb Army chief of staff Gen Radoslav Krstic
Appeals against convictions - 3
On trial - former Yugoslav President Slobodan Milosevic
Cases at pre-trial stage - 9
Still at large - 3 including Radovan Karadzic and Gen Ratko Mladic
Source: International Criminal Tribunal for the Former Yugoslavia
Dutch peacekeepers who were guarding the Srebrenica enclave at the time of the massacre have accepted partial responsibility for what happened.
Mr Karadzic and Gen Mladic have been indicted for genocide but are still at large.
Serbian President Boris Tadic told the Bosnian Serb newspaper Nezavisne Novine that he hoped Gen Mladic would be arrested in the next few days.
Many of the widows attending the ceremony are still waiting to see justice done, says the BBC's Nick Hawton in Srebrenica.
"They killed my entire life and the only thing I want now is to see the guilty ones pay for it," Fatima Budic, whose 14-year-old son Velija was one of the victims, told AP news agency.
Her husband and another son are among the missing.