The United States is offering a $1 million reward for information on Hamza bin Laden, seen here in a video grab by the CIA

The United States on Thursday offered a $1 million reward for information on a son of late Al-Qaeda leader Osama bin Laden, seeing him as an emerging face of extremism.

The location of Hamza bin Laden, sometimes dubbed the "crown prince of jihad," has been the subject of speculation for years with reports of him living in Pakistan, Afghanistan, Syria or under house arrest in Iran.

"Hamza bin Laden is the son of deceased former AQ leader Osama bin Laden and is emerging as a leader in the AQ franchise," a State Department statement said, referring to Al-Qaeda.

The State Department said that it would offer $1 million for information leading to his location in any country.

Bin Laden, who according to the United States is around 30, has threatened attacks against the United States to avenge the 2011 killing of his father, who was living in hiding in the Pakistani garrison town of Abbottabad, by US special forces.

US intelligence agencies increasingly see the younger bin Laden as a successor to his father for the mantle of global jihad, especially as the even more extreme Islamic State group is down to its last sliver of land in Syria.

In 2015, bin Laden released an audio message urging jihadists in Syria to unite, claiming that the fight in the war-torn country paves the way to "liberating Palestine."

And in a message a year later, following in the footsteps of his father, he urged the overthrow of the leadership in their native Saudi Arabia.

Osama bin Laden's three surviving wives and his children were quietly allowed to return to Saudi Arabia after his killing.

But Hamza bin Laden's whereabouts have been a matter of dispute. He is believed to have spent years along with his mother in Iran, despite Al-Qaeda's strident denunciations of the Shiite branch of Islam that dominates the country.

Observers say that the clerical regime in Tehran kept him under house arrest as a way to maintain pressure on rival Saudi Arabia as well as on Al-Qaeda, dissuading the Sunni militants from attacking Iran.

One of Hamza bin Laden's half-brothers told The Guardian last year that Hamza's whereabouts were unknown but that he may be in Afghanistan.

He also said that Hamza bin Laden married the daughter of Mohammed Atta, the lead hijacker in Al-Qaeda's September 11, 2001 attacks on the United States that killed some 3,000 people and sparked the US intervention in Afghanistan.