Saudi Arabia has revoked the citizenship of Hamza bin Laden, the son of the late al-Qaida leader who has become an increasingly prominent figure in the terror network -- and whose whereabouts remains in question, the country announced on Friday.

There was no immediate explanation why the royal decree stripping his citizenship -- signed in November -- was only becoming public now. But the announcement came after the U.S. government on Thursday offered a reward of up to $1 million for information on the son of the Sept. 11 mastermind.

The kingdom similarly stripped Osama bin Laden's citizenship in 1994 while living in exile in Sudan when Hamza bin Laden was a child.

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"This is an example of history rhyming," said Thomas Joscelyn, a senior fellow at the Washington-based Foundation for Defense of Democracies who studies al-Qaida and the Islamic State of Iraq and Syria (ISIS). "He's basically born right after al-Qaida is founded, so his life is totally consumed in the establishment, the formation of al-Qaida and the launching of its war against the West and America."

The State Department said this week, in announcing its $1 million reward, that Hamza bin Laden has urged his followers to launch attacks against the U.S. and its Western allies. Through video and audio messages posted online, he has "threatened attacks" against the U.S. in revenge for his father's killing in May 2011.

As leader of al-Qaida, Osama bin Laden oversaw a series of attacks, including the 1998 bombings of the U.S. embassies in Kenya and Tanzania, as well as the bombing of the USS Cole off Yemen. He and others plotted and executed the Sept. 11, 2001, attacks on New York and the Pentagon, which led to the U.S. invasion of Afghanistan. U.S. Navy SEALs ultimately killed bin Laden in a raid on a house in Abbottabad, Pakistan, in 2011.

Video released by the CIA in 2017 that was seized during the raid shows Hamza bin Laden with a trimmed mustache, but no beard, at his wedding. The State Department said Thursday it believes he married the daughter of Mohamed Atta, the lead hijacker in the Sept. 11 attacks.

"What that would say is that the 9/11 alumni remains very viable and very real even 17 years after the fact," Guardian journalist Martin Chulov told CBSN last summer.

In this image from video released by the CIA, Hamza bin Laden is seen as an adult at his wedding. CIA via AP

Hamza bin Laden is now believed to be around 30. He began appearing in militant videos and recordings in 2015 as an al-Qaida spokesman.

"If you think that your sinful crime that you committed in Abbottabad has passed without punishment, then you thought wrong," he said in his first audio recording.

Joscelyn at the Foundation for Defense of Democracies warned that al-Qaida remains a transnational threat, something that authorities may now pay more attention to as ISIS withers away in Syria.

A United Nations report published last year noted that Hamza bin Laden "continued to emerge as a leadership figure in al-Qaida." It suggested both he and Ayman al-Zawahiri, who took over al-Qaida after Osama bin Laden's death, "are reported to be in the Afghanistan-Pakistan border areas."

"While there is as yet little evidence of a re-emerging direct global threat from al-Qaida, improved leadership and enhanced communication will probably increase the threat over time," the U.N. report said.