RNA - The ruling sparked outrage from Serbian leaders and victims' groups while it was hailed by Bosnian Muslims in the country deeply divided along ethnic lines since its 1992-1995 war.
Oric, 50, was a bodyguard to former Yugoslav president Slobodan Milosevic and is one of only a few Bosnian Muslim commanders to have faced trial for atrocities committed against Serbs.
He was acquitted of killing three ethnic Serb prisoners in 1992. Another Bosnian army soldier, Sabahudin Muhic, was also found not guilty.
The testimony of a protected witness, key for the indictment, lacked credibility and was contradictory, the judge ruled.
"The testimony of witness O-1 ... cannot serve as a credible basis to conclude that Naser Oric committed this murder," judge Saban Maksumic said.
Oric defended the eastern town of Srebrenica, where 8,000 Muslim men and boys were eventually massacred by Serb forces, the worst atrocity in Europe since World War II.
But in 2006, Oric was sentenced by a UN war crimes tribunal to two years in prison for not doing enough to protect Srebrenica's Serb population during Bosnia's 1992-1995 war.
He was acquitted on appeal in 2008, a ruling that angered Serbs, who accused The Hague-based court of "partiality."
Monday's ruling again exposed grievances.
The verdict "is proof that in Bosnia there is no punishment for criminals (committing crimes) against Serbs," Bosnian Serb leader Milorad Dodik said.
"A Muslim (judge) tries a Muslim," he said, suggesting that the ruling would pave the way for a referendum on ethnic Serbs' participation in Bosnia's judicial bodies.
In the past Dodik was repeatedly threatened with an independence referendum for his entity of Republika Srpska, which along with the Muslim-Croat Federation makes up post-war Bosnia.
In Belgrade, Serbian Defense Minister Vulin slammed Oric's acquittal.
"The court which could free a proven criminal, a butcher, Naser Oric, is a court which jeopardizes peace, security, trust, reconciliation in the whole Balkans," Vulin said in a statement.
Oric's acquittal will "radicalize the situation on the political field," Vinko Lale, head of an association of Serb prisoners of war, told AFP.
As a young police officer, Oric was a member of a Belgrade unit tasked with protecting Milosevic, who led the former Yugoslavia's bloody collapse in the 1990s.
Some 130,000 people were killed in the wars that raged on the former federation's territory between 1991 and 1999. Bosnia's conflict claimed 100,000 lives.
When the war between Bosnia's Croats, Muslims and Serbs started, Oric was in his native town of Srebrenica and organized its defense from April 1992.
However he was withdrawn from Srebrenica with several other officers for military training three months before it fell on July 11, 1995.
In Bosnia, many have questioned whether the move was a sign that the authorities had decided to abandon Srebrenica to its fate.
Unhappy with Oric's acquittal by the UN court, Belgrade in 2014 launched an international warrant accusing him of leading "several attacks against Serb villages in the Srebrenica region, to empty them of their Serb population by intimidation, torture and murder."
The victims' associations estimate that 2,428 Serb civilians and soldiers were killed in the area during the 1992-1995 conflict.
Oric was arrested in Switzerland in 2015 on a Serbian warrant but extradited to his country to face charges.
"I have nothing to say, the court said what it had to say," Oric briefly told reporters after leaving the tribunal as he was welcomed by supporters.
"We were expecting such a verdict since this man is not guilty," Kada Hotic, whose son, husband and two brothers were killed in the massacre, told AFP Monday.
After Bosnia's war, Oric kept a low profile until his arrest and transfer to The Hague in 2003.
In 2009, he was sentenced to two years in prison in Sarajevo for illegal arms possession, but was pardoned by the presidency.