Serbian President Boris Tadic has appeared on TV to express deep shock over a gruesome video showing Serbian soldiers killing Bosnian Muslims.
The footage shows victims with their hands tied behind their backs
He said he was ready to visit the town of Srebrenica in July for the 10th anniversary of the massacre in which 8,000 Muslim men and boys were killed.
Mr Tadic was speaking hours after the arrest of at least eight paramilitary troops allegedly shown in the video.
The footage is evidence in the trial of ex-Yugoslav leader Slobodan Milosevic.
"Serbia is deeply shocked," Mr Tadic said in his television address.
"Those images are proof of a monstrous crime committed against persons of a different religion, and the guilty had walked as free men until now."
The amateur footage, showing six civilians with their hands tied behind their backs being lined up and shot, was brought to light by a Serbian human rights organisation.
It was shown at Mr Milosevic's trial in The Hague on Wednesday and later aired by TV stations in Serbia and Montenegro.
Promise on fugitives
Mr Tadic said the crimes at Srebrenica had been carried out "in the name of our nation", but added that crimes were always individual and the perpetrators needed to be punished.
United Nations chief war crimes prosecutor Carla del Ponte, who was in Belgrade, called the arrests a "brilliant operation".
During her visit, the president of Serbia and Montenegro, Svetozar Marovic, vowed that Bosnian Serb leader Radovan Karadzic and former commander Ratko Mladic would be delivered to the war crimes tribunal in The Hague.
Carla Del Ponte wants Karadzic and Mladic to be tried in The Hague
"The Mladic case will be finally successfully concluded within a month so that this heavy load is taken off our backs," Mr Marovic said.
Mladic and Karadzic are the most wanted men in connection with the massacre in Srebrenica. They are believed to be hiding in Serbia and Montenegro or the Bosnian Serb republic.
The video that prompted Thursday's arrests begins with a Serbian Orthodox priest blessing paramilitaries before they go into battle. It ends with what appears to be the same paramilitaries shooting badly beaten civilians prisoners in the back with machine guns.
The killers are wearing the uniforms of a unit known as the Scorpions, which prosecutors say fell under the command of the Serbian interior ministry.
The BBC's Matt Prodger in Belgrade says it is a truly chilling video, and marks the first time that the Serbian media has presented the public with such graphic and direct evidence of the Srebrenica massacre.
Nonetheless, only one newspaper carried the story of the video on its front page on Thursday.
A survey last week suggested that only half the Serbian population believe the Srebrenica massacre actually took place.
The same survey suggested that two-thirds of the public believe Radovan Karadzic and Ratko Mladic are heroes.