The organization reported on Friday field reports written by U.S. soldiers between 2004 and 2009.
The media had advance access to 391,000 documents (The Guardian, New York Times, Al-Jazeera, Der Spiegel and Le Monde) concluded that U.S. Most ignored the allegations of torture, abuse, and even possible murder of hundreds of prisoners by Iraqi forces.
Iraqi courts are based on confessions for convictions which led to frequent allegations of torture.
The New York Times noted that ignoring the majority of cases of abuse amounts to "institutional indifference."
The Times stated that the situation is particularly significant given that the plan to withdraw U.S. troops from Iraq settled in the transfer of security duties to local police and Iraqi Army.
The UN special reporter on torture, Manfred Nowak, and human rights organization Amnesty International today urged the U.S. president, Barack Obama, to open an investigation into the involvement of U.S. forces in human rights abuses in Iraq.
Nowak told the BBC that the U.S. has the moral and legal obligation to investigate credible cases of complicity by U.S. soldiers in torture.
The UN reporter stressed that, if authentic, the documents show clear violations of the UN Convention against torture.
"According to convention, there is the obligation of States to criminalize all forms of torture (...) and of course to investigate any case, bring the perpetrators to justice and provide victims the right to adequate compensation, "said Nowak.
Amnesty International said in a statement that, like the rest of Governments, USA "Has an obligation under international law to ensure that their forces did not use torture and that those detained by U.S. forces are not delivered to authorities as may be tortured."
Malcolm Smart, director of Amnesty's Middle East, insisted that U.S. breached that duty in Iraq despite the "large volume of evidence" that torture is widespread in the country.
From London WikiLeaks founder, Julian Assange, said the documents show "the truth" about the Iraq war.
"We hope to correct some of the attack on the truth that was before the war, during the war and has continued since that officially ended" in late August with the end of U.S. combat operations in that country, said Assange.
The reports also provoked a reaction of the Iraqi government promised to investigate allegations of abuse.
"The government will not show leniency when what is at stake is the right of its citizens," said the office of prime minister Nuri al-Maliki said in a statement.
The prime minister's office, struggling to stay in power after the elections on March 7 failed to produce a clear winner, also stated that the dissemination of an attack on his reelection.
"There are political objectives behind this campaign and some seek to use these documents against national leaders around the prime minister," the statement said.
The White House, meanwhile, remains silent about the leak, which was condemned yesterday by the Pentagon, which said that "there is nothing to indicate the existence of war crimes" but are "300 names of Iraqis in possible danger" at "The country is more vulnerable now."
Earlier, Secretary of State, Hillary Clinton, had condemned "in the clearest terms possible" any leaked documents that "endanger American lives or their allies."
In the same vein the British Government yesterday condemned the release of the documents that he said "may pose a risk to the lives of the troops."
The newly released documents also reveal the death of 15,000 civilians that had not been reported so far.