A UN tribunal at The Hague has found two former Serbian intelligence chiefs not guilty of war crimes and crimes against humanity.
Jovica Stanisic and Franko Simatovic were accused of directing several Serbian units in committing atrocities during the Balkans conflict in the 1990s.
The high-ranking Serb officials, allies of former Yugoslav President Slobodan Milosevic, were accused of training and funding violent paramilitary groups responsible for mass killings and torture during the conflict.
Judges acquitted them on all charges including murder and ethnic cleansing and ordered their immediate release.
Mr Stanisic, 62, was Mr Milosevic's one-time state security chief and seen as one of the country's most powerful men.
Mr Simatovic, 63, a former counter-intelligence officer in the Serbian State Security Services, was transferred to The Hague a decade ago, following the assassination of Serbian Prime Minister Zoran Djindjic.
The International Criminal Tribunal for Yugoslavia (ICTY) said there was insufficient evidence to show that either man had assisted soldiers who were allegedly responsible for murder and other crimes in Bosnia and Croatia.
In summing up, the presiding judge Alphons Orie acknowledged that the crimes had been committed but said there was insufficient evidence to prove the accused were directly responsible.
The verdicts are significant as prosecutors failed to convince the judges that there was any Serbian state responsibility in the mass killings of non-Serbs by the notorious Serb paramilitary brigades, the BBC reports
The ruling comes three months after appeal judges at The Hague acquitted the former chief of the Yugoslav National Army, Momcilo Perisic, of aiding and abetting atrocities by rebel Serbs in Bosnia.