Islamabad (AFP) - Two former senior Pakistani military officials told AFP Tuesday that a defector from Pakistani intelligence assisted the US in its hunt for Osama Bin Laden but denied the two countries had officially worked together.

The officials' accounts come after the publication of a controversial new report by US journalist Seymour Hersh in which he claims to have uncovered a secret deal between the two countries that resulted in the killing of the terror chief in 2011.

The White House has flatly rejected Hersh's claims that Pakistan was told in advance about a 2011 special operations raid that killed Al-Qaeda leader Osama bin Laden.

A source -- who was a serving senior military official at the time of the raid -- told AFP on Tuesday that the defector was a "resourceful and energetic" mid-ranking intelligence officer whose efforts were critical to the success of the raid.

Hersh's report quotes a senior US source as saying a "walk-in" approached the then-CIA station chief in Islamabad in 2010 promising to lead them to bin Laden.

However, the Pakistani military source told AFP the defector had no knowledge his target was bin Laden but was instead given a task that would verify his identity. The source declined to elaborate on what that task was.

"This guy was inducted at a much later stage only to carry out the ground confirmation," the source said. "The US needed a ground confirmation which they couldn't have done without relying on a responsible person."

He added that the defector did not belong to the Inter Services Intelligence (ISI), the country's main spy agency, but another branch, and was now residing in the United States.

Another former official, ex-ISI chief Hamid Gul, told AFP he was also aware of the defector.

"That is in my knowledge, that someone defected," he said. "There was too big a reward, he became a mole and agent to put in practice their plan."

According to Hersh's report, the US learned that Pakistani authorities had bin Laden in their custody and were hoping to use him as a shield against Al-Qaeda and Taliban attacks.

Later, Hersh reported, the US convinced Pakistan to stage a fake raid to kill bin Laden that would be a boost for US President Barack Obama -- then in his first term -- while also allowing the Pakistanis to deny having anything to do with the killing.

Both former Pakistani officials, however, and several other serving officials, have dismissed the allegation that such a deal had been agreed.

After a 10-year manhunt, bin Laden was tracked down to Abbottabad, a garrison town north of Islamabad where Pakistan's military academy is headquartered, sparking allegations authorities were colluding with the terror group.

Qazi Khalilullah, Pakistan's foreign ministry spokesman, meanwhile told AFP Tuesday the government investigating Hersh's account.

"We are looking into the matter and will give our reaction soon," he said.