Prosecutors have made Serbia's first arrests of people suspected of carrying out killings in the 1995 Srebrenica massacre.
Serbian police arrested eight men who are accused of taking part in the slaughter of more than 1,000 Muslims at a warehouse on the outskirts of Srebrenica, a team of Serbian and Bosnian prosecutors said.
Altogether, more than 8,000 Bosnian Muslim men and boys were killed in the eastern Bosnian enclave by the Serbs in 1995 - the only atrocity in Europe to be labelled genocide by the United Nations since the Second World War.
Serbian prosecutors said they initially arrested seven suspects in pre-dawn raids at different locations in Serbia, then caught the eighth suspect later after a manhunt.
Chief Serbian war crimes prosecutor Vladimir Vukcevic said that all those arrested "are former members of a special brigade of the Bosnian Serb police".
Serbia has in the past put on trial men who took a group of prisoners away from Srebrenica to be killed. And in 2011 it arrested Ratko Mladic - the warlord who masterminded the slaughter - and sent him to an international criminal court in The Hague, Netherlands.
But Wednesday's arrests are Serbia's first attempt to bring to justice men who got their hands bloody in the killing machine known as the Srebrenica massacre 20 years ago this July.
"It is important to stress that this is the first time that our prosecutor's office is dealing with the mass killings of civilians and war prisoners in Srebrenica," said Bruno Vekaric, the lead Serb prosecutor in the case.
He said Serbia was approaching a key moment in confronting its past.
"We have never dealt with a crime of such proportions," said Mr Vekaric, Serbia's deputy war crimes prosecutor. "It is very important for Serbia to take a clear position towards Srebrenica through a court process."
Munira Subasic, head of the Mothers of Srebrenica group, called the arrests "good news".
"It was time for Serbia to do something," she said. "This is a message to all criminals who fled and thought they are safe from justice that they can never rest."
The biggest arrest in the sweep was Nedeljko Milidragovic, the commander dubbed Nedjo the Butcher, who went on to become a successful businessman in Serbia.
More than 100,000 people were killed and millions were left homeless in Bosnia's 1992-95 war when Bosnian Serbs, supported by neighbouring Serbia, rebelled against Bosnia's declaration of independence from Serb-led Yugoslavia.
The collaboration by prosecutors from former wartime enemies Serbia and Bosnia - supported by the UN war crimes tribunal - is the most important case of judicial teamwork helping to heal the war's festering wounds.
The arrests follow a December sweep by the same team of prosecutors of 15 suspects in a separate wartime atrocity: a massacre that followed an abduction from a Bosnian train.
Many Serbs still view as heroes their wartime leaders - including Mladic and former Bosnian Serb president Radovan Karadzic, who are on trial at the UN war crimes tribunal - and believe they were victims of a Western plot.
That makes the current campaign to detain the triggermen deeply sensitive. Serbia's conservative government is allowing the prosecutions to move forward in part because it is eager to join the European Union.
That July 1995, Bosnian Serb forces opened the Srebrenica offensive with heavy shelling, ignoring Dutch UN peacekeeping troops stationed in the town. The Serbs - led by Mladic - marched into the town without meeting any resistance. Women sought shelter at the Dutch base, while Bosnian men and boys fled into the surrounding woods and were hunted down by Mladic's forces.
The men and boys captured by Milidragovic's men were rounded up and crammed tight into the warehouse with no food or water. There was not even enough room for everyone to sit as they waited in fear. The slaughter started in the late afternoon, when the killers hurled bombs through the windows and fired round after round of automatic gunfire.
In the morning, witnesses say, Milidragovic ordered the survivors - up to 100 of them - to come out, promising they would be spared. They were not.
Even his troops said they were terrified of the commander.
"I was afraid to look him in the eyes," one of them, a protected witness, said in a deposition.
When the Bosnian war ended in a peace deal in 1995, Milidragovic moved to the Serbian capital, Belgrade. He had two children and built a trucking business that transports construction material - prosecutors say his start-up capital came from tens of thousands of dollars taken from his victims' pockets. He is now 58.