"Difficult days are ahead of us ... It is of crucial importance to keep the peace and to stabilize the entire territory of the province (Kosovo)," he added. "It is crucial that our citizens do not react to provocations."
Some tried to cool things down.
"Serbia needs to acknowledge reality in the region, which means also Kosovo's independence and really to proceed with constructive regional policy," Sonja Biserko, president of the Helsinki Committee for Human Rights in Serbia told ABCNews.com.
But many Serbs, it is a difficult thing to accept.
Tens of thousands of ethnic Serbs fled Kosovo after the war and many still live in refugee camps in Serbia. One of those refugees, Snezana Petrovic, came to a prayer for Kosovo at Belgrade's mammouth St Sava Church.
"It's very hard to think about it. Still now I can't believe that I'm not living in my own country anymore," she says. "I feel like I'm a guest here. I still see Kosovo as a part of Serbia. Our roots and our hearts are there."
Retired historian Sava Vukicevic said, "History is obsession with the Serbs. Everyone is familiar with painting of withdrawal from Kosovo Polje in 1389, when Serbs lost to Ottoman Turks. It always has to be dramatic. The bells toll are commemorating yet another defeat but it is now a modern battle fought at the court room in the Hague."