The UN chief prosecutor in The Hague has condemned Serbia's failure to hand over Gen Ratko Mladic as seven other Bosnian Serbs face the judges again.
Srebrenica was Europe's worst atrocity since World War II
"Mladic should be on trial for this case," Carla del Ponte said, presenting the prosecution case against the seven on trial for the Srebrenica massacre.
It is the biggest joint trial yet over the 1995 massacre of Bosnian Muslims.
About 8,000 men and boys sheltering in a UN-designated safe area were killed by Bosnian Serb troops.
The seven Bosnian Serb army officials on trial are charged with genocide and war crimes.
The accused men all deny the charges against them.
As the trial resumed on Monday, Ms del Ponte said it was inexcusable that Serbia had not arrested Gen Mladic, accused of masterminding the massacre.
"The government of Serbia is perfectly capable of doing so... It is absolutely scandalous," she said.
Gen Mladic and the former Bosnian Serb political leader Radovan Karadzic are the most wanted fugitives in connection with the Balkan wars of the 1990s.
Vujadin Popovic: Bosnian Serb commander
Ljubisa Beara: Chief of staff
Drago Nikolic: Security chief
Ljubomir Borovcanin: Special police commander
Radivoje Miletic: Deputy chief of staff
Milan Gvero: Assistant commander
Vinko Pandurevic: Brigade commander
The men on trial include Ljubisa Beara, the former security chief of the Bosnian Serb army.
"It is difficult, if not impossible to comprehend the horror inflicted on the inhabitants of the Srebrenica enclave," Ms del Ponte said.
The trial is being seen as a significant step in judging the worst atrocity in Europe since World War II.
The prosecution insisted on a joint trial to save time and to avoid witnesses giving repeated testimony.
Last week, a forensic team finished exhuming the remains of more than 1,000 victims from the massacre, found in a single grave near the village of Kamenica in eastern Bosnia.
Gen Mladic's deputy, Gen Radislav Krstic, is serving a 35-year prison term for his role in the massacre. Col Vidoje Blagojevic is appealing against his 18-year sentence for complicity in genocide.