After Seymour Hersh claimed in a lengthy exposé  that the Obama administration inaccurately took full credit for the killing of Osama bin Laden, more sources have come forward to confirm his account.

Two intelligence sources have told NBC News that the year before the U.S. raid that killed Osama bin Laden, a "walk in" asset from Pakistani intelligence told the CIA where bin Laden was hiding, while three sources say that the Pakistani government was aware of bin Laden's location all along.

Hersh, quoting a single, unnamed source in his article, said that the Pakistani government had an active role in approving and implementing the raid in Abbottabad, Pakistan, where bin Laden died.

The source also said that the CIA and United States learned about bin Laden's location after paying a former senior Pakistani intelligence officer a $25 million reward for the information.

The Obama administration's version claimed that the Pakistani government had no involvement, was unaware of the attack in advance, and that bin Laden had been tracked down through his couriers, not through the reward.

On Monday, Pentagon spokesman Col. Steve Warren said Hersh's piece was "largely a fabrication" and that there were "too many inaccuracies" to detail each one, NBC reported.

Warren said the raid to kill bin Laden was a "unilateral action."

Both the National Security Council (NSC) and the Pentagon denied that Pakistan had played any role in the raid.

"The notion that the operation that killed Osama bin Laden was anything but a unilateral U.S. mission is patently false," said NSC spokesman Ned Price. "As we said at the time, knowledge of this operation was confined to a very small circle of senior U.S. officials."

The administration's statements refuting the account make no mention of a "walk-in" source, NBC said.

Others close to the administration have hit back at the claims in Hersh's article.

"If you were to believe Sy, you would have to believe this massive conspiracy that President Obama, Robert Gates, Leon Panetta and Mike Morell were all lying to you," Bill Harlow, the CIA's former top spokesman, told Politico. "It makes absolutely no sense."

One former intelligence official knowledgeable about the bin Laden raid also called Hersh’s report "a fictional account," according to Politico.

"This was indeed a unilateral American operation, one that involved months of painstaking intelligence analysis, and the Pakistanis were never read in on the raid before it happened."

John McCain, chairman of the Senate Armed Services Committee, dismissed Hersh's account. "I simply have never heard of anything like this and I've been briefed several times," said the Arizona Republican, according to NBC News.

"This was a great success on the part of the administration and something that we all admire the president's decision to do."

For his part, Hersh has defended his account.

He told CNN on Monday, "I've been around a long time … and I understand the consequences of what I'm saying." 

Related Stories:

• Bin Laden Killer O'Neill: Seymour Hersh Story 'Ludicrous'
• White House Denies Pakistan Had Role in Bin Laden Raid