NEW YORK - A prominent human rights group is calling on the U.S. Department of Justice to investigate why the administration of former President George W. Bush blocked three different probes into war crimes in Afghanistan where as many as 2,000 surrendered Taliban fighters were reportedly suffocated in container trucks and then buried in a mass grave by Afghan forces operating jointly with U.S. forces.

The Boston-based Physicians for Human Rights (PHR), which discovered the mass gravesite in 2002, has issued the call for the criminal probe. The organisation says U.S. government documents it has obtained show that the bodies were reportedly buried in mass graves in the Dasht-e-Leili desert near Sheberghan, Afghanistan.

It charges that Afghan warlord General Abdul Rashid Dostum, who it says was on the payroll of the U.S. Central Intelligence Agency (CIA), was responsible for the massacre.

"Physicians for Human Rights went to investigate inhumane conditions at a prison in northern Afghanistan, but what we found was much worse," stated Susannah Sirkin, PHR's deputy director.

"Our researchers documented an apparent mass grave site with reportedly thousands of bodies of captured prisoners who were suffocated to death in trucks. That was 2002; seven years later, we still seek answers about what exactly happened and who was involved," she said.

PHR says senior Bush administration officials impeded investigations by the Federal Bureau of Investigation (FBI), and the State and Defence departments, and apparently never conducted a full inquiry. The New York Times made the disclosure earlier this month in a story by Pulitzer Prize-winning reporter James Risen.

Subsequently, President Barack Obama told CNN's Anderson Cooper that he has directed his national security team to look into the alleged massacre. Obama said the government needs to find out whether actions by the U.S. contributed to possible war crimes.

"The Bush administration's disregard for the rule of law and the Geneva Conventions led to torture of prisoners in Guantánamo and many other secret places," noted Nathaniel Raymond, PHR's lead researcher on Dasht-e-Leili.

"Contrary to the legal opinions of the previous Department of Justice, the principles of the Geneva Conventions are non-negotiable, as is their enforcement. President Obama must open a full and transparent criminal probe and prosecute any U.S. officials found to have broken the law," he said.

"The State Department's statement to the New York Times that suspected war crimes should be thoroughly investigated indicates a move towards full accountability," added Raymond. "We stand ready to aid the U.S. government in investigating this massacre. It is time for the cover-up to end."

PHR reiterated its call to the government of Afghanistan, which has jurisdiction over the alleged mass grave site, to secure the area with the assistance of ISAF (International Security Assistance Force-Afghanistan), protect witnesses to the initial incident and the ensuing tampering, and ensure a full investigation of remaining evidence at the site, including the tracing of the substantial amount of soil that appears to have been removed in 2006.

"Gravesites have been tampered with, evidence has been destroyed, and witnesses have been tortured and killed," PHR said. "The Dasht-e-Leili mass grave site must finally be secured, all surviving witnesses must be protected, and the government of Afghanistan, in coordination with the U.N. and NATO (North Atlantic Treaty Organisation), must at last allow a full investigation to go forward."

PHR charged that U.S. officials have been reluctant to pursue an investigation - sought by officials from the FBI, the State Department, the Red Cross and human rights groups - because the warlord, Gen. Abdul Rashid Dostum, was on the payroll of the CIA and his militia worked closely with U.S. Special Forces in 2001.

The group said the United States also worried about undermining the U.S.-supported government of President Hamid Karzai, in which General Dostum had served as a defence official.

"At the White House, nobody said no to an investigation, but nobody ever said yes, either," said Pierre Prosper, the former U.S. ambassador for war crimes issues. "The first reaction of everybody there was, 'Oh, this is a sensitive issue; this is a touchy issue politically'."

PHR's Raymond, who is head of the organisation's Campaign Against Torture, told IPS that President Obama's statement was welcome.

But, he added, "The president's rhetoric must be matched by urgent action. He needs to pressure President Karzai to secure the mass graves site, protect witnesses and make sure that U.S.-led military forces and the United Nations in Afghanistan protect all evidence of the crimes."

PHR said that, in recent weeks, State Department officials have quietly tried to thwart General Dostum's reappointment as military chief of staff to the Afghan president, according to several senior officials, and suggested that the administration might not be hostile to an inquiry.

The question of culpability for the prisoner deaths - which may have been the most significant mass killing in Afghanistan after the 2001 U.S.-led invasion - has taken on new urgency since the general, an important Karzai ally, was reinstated to his government post last month. He had been suspended last year and living in exile in Turkey after he was accused of threatening a political rival at gunpoint.

The killings reportedly occurred in late November 2001, just days after the U.S.-led invasion forced the ouster of the Taliban government in Kabul. Thousands of Taliban fighters surrendered to General Dostum's forces, which were part of the U.S.-backed Northern Alliance, in the city of Kunduz. They were then transported to a prison run by the general's forces near the town of Shibarghan.

Survivors and witnesses told The New York Times and Newsweek in 2002 that over a three-day period, Taliban prisoners were stuffed into closed metal shipping containers and given no food or water; many suffocated while being trucked to the prison. Other prisoners were killed when guards shot into the containers.

General Dostum, however, has said previously that any such deaths of the Taliban prisoners were unintentional. He has said that only 200 prisoners died and blamed combat wounds and disease for most of the fatalities.

The first calls for an investigation came from PHR and the International Committee of the Red Cross. A military commander in the United States-led coalition rejected a request by a Red Cross official for an inquiry in late 2001, according to the official, who, in keeping with his organisation's policy, would speak only on condition of anonymity and declined to identify the commander.

Subsequently, PHR asked the Defence Department to investigate the alleged massacre, but no action was taken. PHR says the prisoner deaths came up in a conversation with Paul D. Wolfowitz, the deputy secretary of defence at the time, in early 2003.

"Somebody mentioned Dostum and the story about the containers and the possibility that this was a war crime. And Wolfowitz said we are not going to be going after him for that," according to the group.