One of Osama bin Laden's sons "may be dead," a US counterterrorism official told AFP Thursday, after reports he was likely killed by a US missile strike in Pakistan earlier this year.

"There are some indications that he may be dead, but it's not 100 percent certain," the official said. "If he is dead, Saad bin Laden was a small player with a big name. He has never been a major operational figure."

An administration official said the Al-Qaeda leader's third-oldest son "was likely killed in Pakistan."

National Public Radio reported Wednesday that Saad bin Laden was killed in Pakistan by Hellfire missiles fired from a US Predator drone "sometime this year."

US spy agencies are "80 to 85 percent" sure Saad bin Laden is dead, a senior counterterrorism official told NPR, acknowledging it was difficult to be completely sure without a body to conduct DNA tests on.

It was unclear whether Saad bin Laden was close to the location of his father, who is believed to be hiding in the rugged mountainous tribal belt along the Afghanistan-Pakistan border, when he died.

According to the US Treasury, Saad bin Laden, who is believed to have been in his 20s, was part of a small group of Al-Qaeda operatives who helped manage the organization from Iran, where he was arrested in 2003.

He also allegedly helped facilitate communications between Al-Qaeda's number two leader, Ayman al-Zawahiri, and the Quds Force, an elite unit of Iran's Revolutionary Guards, following an Al-Qaeda attack on the US embassy in Yemen in 2008.

In January, in the dying days of the administration of president George W. Bush, the US Treasury Department froze the assets of Saad bin Laden and three other Al-Qaeda operatives.

The last audio message said to be from Osama bin Laden and released by Al-Qaeda was aired in June on Al-Jazeera when he accused President Barack Obama of following Bush's policy in "antagonizing Muslims."

And although Obama has vowed to hunt down bin Laden, the Al-Qaeda leader continues to elude any captors.

Washington has placed Pakistan at the heart of the fight against Al-Qaeda and the Taliban, and Obama has ordered an extra 21,000 troops to neighboring Afghanistan in a bid to stabilize the country for August elections.

The US military and the Central Intelligence Agency (CIA) are the only forces to deploy drones to the region.(AFP)