It is not known if Osama Bin Laden was in the same location as his son
US defence officials say they are all but certain that Osama bin Laden's son, Saad, was killed by a US missile strike in Pakistan earlier this year.
The Pentagon would say nothing in public, but officials in Washington speaking anonymously said they thought it very likely Saad bin Laden was dead.
Saad Bin Laden - Osama Bin Laden's third son - is in his late 20s.
Correspondents say he is believed to have been active in al-Qaeda but never a senior lieutenant to his father.
Intelligence agents were "80 to 85%" sure Saad Bin Laden had been killed, an official told the US-based National Public Radio.
"We make a big deal out of him because of his last name," the official said.
US intelligence agencies believe Saad Bin Laden fled to Pakistan after spending several years under house arrest in Iran.
He was not targeted but was caught in a missile strike from an unmanned American drone flying over Pakistan "sometime this year", an official told NPR.
He was probably killed by a Hellfire missile fired from a US Predator drone, the official said.
It is not known if he was in the same location as his father, who is believed to be hiding in the rugged mountainous tribal area that runs along the Pakistan-Afghanistan border.
The US has stepped up its drone attacks on targets linked to al-Qaeda and Taliban militants in the area.
It is a tactic started under former President George W Bush, but embraced by President Barack Obama, says the BBC's Adam Brookes in Washington.
US officials maintain that in the absence of concerted Pakistani help in the hunt for Osama bin Laden, the use of unmanned drones is their best option, our correspondent adds.