National Public Radio, a US radio service, reported on Wednesday that Saad bin Laden, Osama bin Laden’s third-oldest son, died in an air raid "sometime this year."

US spy agencies are "80 to 85 per cent" sure that Saad bin Laden is dead, a senior counterterrorism official told NPR.

It is not clear whether Osama bin Laden was in the vicinity of his son when the raid was launched.

Iran link

The US Treasury has alleged that Saad bin Laden was involved in a group of al-Qaeda members who assisted with managing the organisation from Iran.

He allegedly helped provide communications between Ayman al-Zawahiri, al-Qaeda's deputy leader, and the al-Quds Force, an elite unit of Iran's Revolutionary Guards, after an al-Qaeda attack on the US embassy in Yemen in 2008.

Barack Obama, the US president, has said that the hunt for Osama bin Laden is continuing but intelligence officials have been unable to pinpoint his location.

Bin Laden is believed to be sheltering in the mountainous Pakistan-Afghanistan border region, an area that is notoriously difficult for foreign forces to navigate and operate in.

Obama has placed security in Afghanistan and neighbouring Pakistan at the centre of his foreign policy strategy.

He recently ordered an extra 21,000 troops to Afghanistan in a fresh push against fighters loyal to the Taliban and al-Qaeda, and has urged Pakistan's government to crack down on armed groups on its soil, particularly those operating in the border regions.

The US military and the Central Intelligence Agency (CIA) have each deployed pilotless drones to the region.

Islamabad publicly opposes the US air raids, calling them a violation of its territorial sovereignty and criticising their high civilian death toll.