hamza bin laden
Picture taken from Al Jazeera television purportedly shows Hamza bin Osama bin Laden (C), one of the sons of Saudi-born dissident Osama bin Laden, seated between two Taliban fighters near Ghazni, Afghanistan.Reuters

Hamza bin Laden, son of the 9/11 mastermind, and late al-Qaida leader Osama bin Laden, has promised to avenge his father's assassination by threatening the United States through an 21 minute audio message posted online titled "We Are All Osama."

"As for the revenge by the Islamic nation for Sheikh Osama, may Allah have mercy on him. It is not revenge for Osama the person, but it is revenge for those who defended Islam." Hamza, who made his first radio appearance last year through Ayman al-Zawahiri in a bid to recruit more younger militants, was quoted saying by The Guardian.

"Hamza provides a new face for al-Qaida, one that directly connects to the group's founder. He is an articulate and dangerous enemy," Bruce Riedel, leading expert on U.S. security from the Brookings Institute was quoted as saying.

Hamza is also believed to have been by his father's side in Afghanistan before the 9/11 attacks and subsequently migrated to Pakistan after the US pressure pushed senior al-Qaida's leadership.

Hamza bin Laden, now in his mid-20s promised to continue the global militant group's fight against the United States and its allies, according to the SITE Intelligence Group.

"We will continue striking you and targeting you in your country and abroad in response to your oppression of the people of Palestine, Afghanistan, Syria, Iraq, Yemen, Somalia and the rest of the Muslim lands that did not survive your oppression," Hamza added.

Documents, recovered from bin Laden's secret compound after US commandos infiltrated and executed him, revealed last year that his men had attempted to reunite the father and son. They were unable to do so as Hamza was under house arrest in Iran at the time.