WASHINGTON -- President Obama has ordered his national security team to investigate reports that U.S. allies were responsible for the deaths of as many as 2,000 Taliban prisoners of war during the opening days of the war in Afghanistan.

Obama told CNN in an interview that aired Sunday that he doesn't know what how the U.S.-allied Northern Alliance behaved in November 2001, but he wants a full accounting before deciding how to move forward.

"I think that, you know, there are responsibilities that all nations have even in war," Obama said during an interview at the end of a six-day trip to Russia, Italy and Ghana.

"And if it appears that our conduct in some way supported violations of the laws of war, then I think that, you know, we have to know about that."

The president's comments seem to reverse officials' statements from Friday, when they said they had no grounds to investigate the 2001 deaths of Taliban prisoners of war who human rights groups allege were killed by U.S.-backed forces.

Reacting to the interview, Physicians for Human Rights hailed Obama's decision.

"President Obama is right to say that U.S. and Afghan violations of the laws of war must be investigated," said Nathaniel Raymond, a Physicians for Human Rights researcher. "If the Obama administration finds that criminal wrongdoing occurred in this case, those responsible -- whether American or Afghan officials -- must be prosecuted."

But Obama's direction -- discussed as he toured a former slave castle on Ghana's coast -- does not guarantee action.

"We'll probably make a decision in terms of how to approach it once we have all the facts gathered up," Obama said.

The mass deaths were brought up anew Friday in a report by The New York Times. It quoted government and human rights officials accusing the Bush administration of failing to investigate the executions of hundreds, and perhaps thousands, of prisoners.

U.S. officials said Friday they did not have legal grounds to investigate the deaths because only foreigners were involved and the alleged killings occurred in a foreign country.

The Times pointed to U.S. military and CIA ties to Afghan Gen. Abdul Rashid Dostum, accused by human rights groups of ordering the killings. The newspaper said the Defense Department and FBI never fully investigated the incident.

The allegations date back to November 2001, when as many as 2,000 Taliban prisoners died in transit after surrendering during one of the regime's last stands, according to a State Department report from 2002.

Witnesses have claimed that forces with the U.S.-allied Northern Alliance placed the prisoners in sealed cargo containers over the two-day voyage to Sheberghan Prison, suffocating them and then burying them en masse, using bulldozers to move the bodies, according to the State Department report. Some Northern Alliance soldiers have said that some of their troops opened fire on the containers, killing those within.

Dostum, the Northern Alliance general who is accused of overseeing the atrocities, has previously denied the allegations. He was suspended from his military post last year on suspicion of threatening a political rival, but Afghan President Hamid Karzai recently rehired him.