Russia has vetoed a United Nations resolution that would have described the 1995 massacre in Srebrenica as "genocide."
Four other countries at the Security Council, Angola, China, Nigeria, and Venezuela, abstained from the July 8 vote.
The remaining 10 council members voted in favor of the British-drafted resolution that aimed to mark 20 years since the worst massacre in Europe since World War II.
The draft said that "acceptance of the tragic events at Srebrenica as genocide is a prerequisite for reconciliation."
Two international courts and many officials at the UN have used the term genocide to describe the massacre of 8,000 Muslim men and boys at Srebrenica, which occurred amid the breakup of Yugoslavia.
But that term offends Serbia and Bosnian Serbs, who have asked Moscow to ensure it is taken out of the UN measure.
After Russia vetoed the draft resolution, Serbian President Tomislav Nikolic said, "Not only was the stigmatization of the entire Serbian people as genocidal prevented, but Russia today showed and proved that it has been a real and honest friend."
"This is a great day for Serbia," the statement added.
Addressing the Security Council session that began with a minute of silence to remember the victims, Russia's UN Ambassador Vitaly Churkin called the text "not constructive, confrontational, and politically motivated," and argued that it unfairly singled out Bosnian Serbs for war crimes.
"The draft that we have in front of us will not help peace in the Balkans but rather doom this region to tension," he added.
British Deputy Ambassador Peter Wilson accused Moscow of siding "with those who are unwilling to accept the facts today."
"Russia's actions tarnish the memory of all those who died in the Srebrenica genocide," he said.
"Russia's veto is heartbreaking for those families [of the victims] and it is a further stain on this council's record," said U.S. Ambassador to the UN, Samantha Power, who worked as a journalist during the Bosnian war.
Srebrenica Mayor Camil Durakovic said, "This is a defeat of justice."
And in Sarajevo, Munira Subasic, the head of the Mothers of Srebrenica group, said that Russia “showed that it backed the crime instead of justice."
The vote at the Security Council, originally scheduled for July 7, had been delayed and then postponed to give Britain, Russia, and United States time to try to find compromise language.
The disagreement over the text revived divisions from the Balkan wars when Russia sided with Bosnian Serbs and Serbia, while Western countries supported Bosnian Muslims and Croatia.
Also on July 8 in Bosnia-Herzegovina, several thousand people began an annual 100-kilometer march to commemorate the victims of the Srebrenica massacre.
Participants in the three-day march are tracing the path taken by Bosnian Muslim men and boys fleeing Bosnian Serb forces who were advancing toward the United Nations protected area at Srebrenica on July 11, 1995.
But the commemorative march is heading in the opposite direction -- starting from Nezuk near the eastern town of Tuzla and moving toward Srebrenica.
They are due to arrive at a Srebrenica memorial center in Potocari on July 11 for a 20th anniversary commemoration of the massacre.
On July 7, Serbian Prime Minister Aleksandar Vucic said he will attend the commemoration after he received assurances that no resolution that is "humiliating" for Serbia and the Serb Republic in Bosnia will be adopted.
Serbia in 2010 acknowledged that a "grave crime" took place in Srebrenica and condemned the massacre, as it sought closer ties with the West, but stopped short of calling it a genocide.
