It is the biggest ever joint trial for war crimes committed during the Balkan wars in the 1990s.

Seven of the key men allegedly behind the murder of nearly 8,000 Muslim men and boys by Bosnian Serb forces in July 1995 will be tried.

Five of the seven face charges of genocide as well as war crimes and crimes against humanity. All have pleaded not guilty.

However, the two most important indicted suspects, Radovan Karadzic, the former Bosnian Serb leader, and Ratko Mladic, his military commander, remain at large, 11 years after the massacre.

Nevertheless, the case at the Hague-based International Criminal Tribunal for the former Yugoslavia is seen as a significant step in judging the single worst atrocity in Europe since World War II, the only one the court has ruled as genocide.

The trial formally opened on July 14, but that hearing was devoted to procedural matters before the court went into its summer recess.

The defendants facing genocide charges are Ljubisa Beara, the chief of security of the main staff of the Bosnian Serb army, Vujadin Popovic, an officer allegedly responsible for managing the military police, Ljubomir Borovcanin, the deputy commander of the Bosnian Serb special police, Vinko Pandurevic, the commander of the brigade that led the attack and Drago Nikolic, the brigade's chief of security.

The other two men are charged with war crimes and crimes against humanity, being responsible for blocking aid and supplies to Srebrenica.

From 1993, when it came under UN protection, the enclave of  Srebrenica in eastern Bosnia was flooded by thousands of Muslim  refugees driven from their homes by a Bosnian Serb offensive.

On July 11 1995, Bosnian Serb forces finally overran the town,  separating women and children from the men and boys they deemed to be of fighting age.

More than 8,000 men and boys were summarily executed at several  locations around Srebrenica. The lightly armed Dutch peacekeepers protecting the enclave failed to act against the executions.