Serbia is protesting an attack Saturday on its prime minister at a ceremony marking the 20th anniversary of the Srebrenica massacre, calling it an "assassination attempt" and demanding a formal apology from Bosnia-Herzegovina.
The attack came moments after Prime Minister Aleksandar Vucic entered a cemetery near the enclave to lay flowers commemorating the slaughter of 8,000 Muslim men and boys by Bosnian Serbs toward the end of the 1992-95 war.
Vucic, once a Serbian ultranationalist who supported Bosnian Serbs in the conflict, attended the ceremony in an apparent gesture of reconciliation. Both he and his entourage were bombarded with stones and other objects. The prime minister escaped the scene with broken eyeglasses and minor facial injuries.
The Muslim Bosniak mayor of Srebrenica, Camil Durakovic, said he was "deeply disappointed and I truly apologize to Prime Minister Vucic for what he experienced."
Council of Europe Secretary General Thorbjorn Jagland condemned the attack.
The ceremony in Potocari "should have been a place for reflection, reconciliation, not violence," Jagland said.
WATCH: Serbian PM Attacked at Srebrenica Event
Former U.S. President Bill Clinton and other world dignitaries also attended the ceremonies and laid flowers at the memorial without incident.
"I grieve that it took us so long to unify ... to stop this violence," said Clinton, who was in office at the time of the massacre.
Clinton said before the attack on Vuvic: "I want to thank the prime minister of Serbia for having the courage to come here today, and I think it is important that we acknowledge that."
Authorities billed Vucic's presence as a measure of how much the region has healed since the breakup of the former Yugoslavia and the outbreak of war that gripped the region in its aftermath.
But the visit came just days after the Vucic government asked ally Russia to veto a United Nations resolution that would have condemned Serbia for insisting that the killings did not qualify as genocide.
Saturday's memorial ceremonies, attended by tens of thousands of mourners, came ahead of the burial of 136 newly identified victims of the killings — the worst mass killings on the European continent since the end of World War II. Thousands more victims already are interred at the Potocari Memorial Cemetery outside Srebrenica.
On July 11, 1995, Bosnian Serb forces overran the U.N. enclave at Srebrenica, which was nominally protected by Dutch troops, and launched days of bloodshed. Serbs dumped their victims in mass graves around Srebrenica in an effort to hide the magnitude of the slaughter.
In a statement, President Barack Obama said the world "can offer no solace that fully addresses the pain borne by the victims’ families. But we must look back at Srebrenica with clear eyes, commemorate the tragedy and learn from it."
The Dayton Accords brokered in the 1990s by U.S. negotiators formally ended the Bosnian war, which claimed 100,000 lives.
Some material for this report came from AP.