On Saturday, crowds chased Serbian prime minister Aleksandar Vucic away from a memorial service at a graveyard in Bosnia-Herzegovina, where tens of thousands of people had gathered to mark the 20th anniversary of the Srebrenica massacre.

Over four days in July 1995, after they took the town of Srebrenica, which the United Nations had designated a “safe area,” Bosnian Serb death squads murdered eight thousand Bosnian Muslim men and boys. According to CBS News:

During the war, the United Nations declared Srebrenica a safe haven for civilians. But on July 11, 1995, Serb troops overran the Muslim enclave. Some 15,000 men tried to flee through the woods toward government-held territory while others joined the town’s women and children in seeking refuge at the base of the Dutch U.N. troops.

The outnumbered Dutch troops could only watch as Serb soldiers rounded up about 2,000 men for killing and later hunted down and killed another 6,000 men in the woods.

Bodies are still being discovered. On Saturday, the Guardian reports, 136 newly found victims were buried alongside a mass grave of more than 6,000. At least 1,000 bodies are yet to be located.

During the war, CBS reports, Vucic was an ultranational politician who criticized the late Slobodan Milosevic for his leniency towards Bosnian Muslims. According to Reuters, at the ceremony on Saturday, some held up a banner displaying a quote attributed to Vucic: “For every Serb killed, we will kill 100 Muslims.”

Vucic arrived at the graveyard with a delegation to lay flowers. The Guardian reports that people in the crowd booed and whistled, while others shouted, “Genocide!” Eventually, people began throwing things.

“We were attacked from all sides. It was well organized and prepared,” Vucic said, according to CBS. He blamed hooligan soccer groups. “Except for my glasses, I’m missing nothing else.” The Serbian interior minister, Nebojsa Stefanovic, described the attack as an “assassination attempt.”

Serbia and Bosnian Serbs still deny that what took place in Srebrenica was genocide, CBS reports, and also claim that the number of dead has been exaggerated.

Photo credit: AP Images. Contact the author of this post: brendan.oconnor@gawker.com.