Hamza bin Laden

The US official, who spoke on condition of anonymity, provided no further details, including when Hamza died or where.

President Donald Trump earlier declined to comment after NBC News first reported the US. assessment Asked if he had intelligence that bin Laden's son had been killed, Mr Trump told reporters: "I don't want to comment on it."

White House national security adviser John Bolton also refused to comment.

Separately, the White House declined comment on whether any announcement was imminent.

Hamza, who is now in his late 20s, was named an official member of al-Qaeda in 2015 and is seen as a possible successor to his father.

Since then, he has called for attacks against western capitals.

The US State Department said it was notifying the international community that "Hamza bin Laden is actively engaged in terrorism".

The official sanction blocks him from any business dealings with US companies or holding property on US soil.

'Charismatic, popular'

Hamza bin Laden, believed to be in his mid-20s and reportedly known as the ‘crown prince of terror’, has been touted as a future leader of al-Qaeda.

In the message, which was shared on Twitter, he calls for lone wolf jihadist attacks on America and its allies and marks out London, Washington, Paris and Tel Aviv as specific  targets.

The message made no mention of Isis.

Rita Katz, director of Site, a terror intelligence group, tweeted: "Hamza Bin Laden, son of Usamah bin Laden [sic], gives strategies in continuing global jihad in audio message.