As the Balkan nation observed a day of mourning, some 50,000 people, including world leaders, gathered to commemorate the 20^th anniversary of the Srebrenica massacre which saw thousands of Muslims killed over five July days.

Bill Clinton, who was US president at the time of massacre, Turkish Prime Minister Ahmet Davutoglu, Britain's Princess Anne and Jordan's Queen Noor are among the dignitaries who attended the memorial service.

At a ceremony later on Saturday, families will bury the remains of some 136 people who died during the war next to the graves of over 6,000 previously found Srebrenica victims.

'Monstrous crime'

Prior to the service, Serbian Prime Minister Aleksandar Vucic condemned the Srebrenica massacre as a "monstrous crime."

"There are no words to express regret and pain for the victims as well as anger and bitterness towards those who committed the monstrous crime," Aleksandar Vucic said in a statement prior to attending the ceremony in the eastern Bosnian town on Saturday.

"Serbia clearly and unambiguously condemns this horrible crime and is disgusted with all those who took part in it and will continue to bring them to justice," he added.

Saturday marks the 20th anniversary of the killings of some 8,000 Muslims by Bosnian Serb forces which took place toward the end of Bosnia's 1992-95 war.

Bosnian Serb troops, led by General Ratko Mladic - who is currently on trial in The Hague - overran Srebrenica in July 1995, while it remained an enclave within Serb-held territory. Some 25,000 people remained in the town, seeking help from Dutch UN peacekeepers. The UN soldiers were outnumbered and the Serb forces immediately slaughtered some 2,000 men and boys, before pursuing and killing some 6,000 more who fled into the forests.

A 'genocide'

Thousands of Srebrenica survivors and other people walked to the site in the days leading up to the anniversary.

"It took me seven days to reach Nezuk (after escaping Srebrenica). It was horrible…dead people, blood everywhere. I saw my neighbors, friends, relatives, but they couldn't be helped," one march participant, Nedzad Mujic, told the AFP news agency.

On Wednesday, Russia vetoed a UN resolution recognizing the Srebrenica massacre as genocide, claiming it would create divisions in the Balkans. Britain, which put forward the resolution, condemned the move as outrageous.

The vetoed resolution stated that acceptance of "the tragic events at Srebrenica as genocide is a prerequisite for reconciliation" and condemned "denial of this genocide as hindering efforts towards reconciliation."

Hearings at the International Criminal Tribunal for the former Yugoslavia and International Criminal Court both declared the 1995 slaughter of Muslim boys and men as genocide.

shs/jlw (AFP, AP)