Iran is believed to be housing the "uncontested" new leader of the al-Qaeda terrorist organization a report by the U.N. said this week.

Saif al-Adel, a former Egyptian special forces officer and prominent member of the insurgent group with a $10 million U.S.-bounty on his head, is believed to be the new unofficial leader of al-Qaeda.

The group has not officially named a successor following the 2022 killing of then-leader Ayman al-Zawahiri. 

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The death caused a significant blow to al-Qaeda which had not lost a leader since Osama bin Laden was killed by U.S. special forces in May 2011. 

The U.S. on Wednesday backed the U.N.'s assertions, and State Department press secretary Ned Price told reporters that Tehran’s offer of safe haven to a designated terrorist is "just another example of Iran’s wide-ranging support for terrorism" and "it's destabilizing activities in the Middle East and beyond."

Al-Adel is also wanted in coordination with the 1998 embassy bombings in Kenya and Tanzania. 

The Iran Mission to the U.N. responded to the accusations in a tweet and claimed that al-Qaeda was dismantled following the death of bin Laden more than a decade ago and said the group "is no longer in existence, but its extremist ideology still persists."

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"It is worth noting that the address for the so-called newly appointed al-Qaeda leader is incorrect," the Iranian comment added. "This misinformation could potentially hinder efforts to combat terrorism."

The once-believed degree of separation when it came to Iran – which predominately adheres to Shia Islam – and Sunni-based terrorist groups like al-Qaeda or the Taliban is an old "trope," one expert told Fox News Digital.

"This has been a long-standing trope within the diplomatic and intelligence field that Iran versus Sunni and the Shia can't cooperate," senior fellow and editor of the Foundation for Defense of Democracy's (FDD) Long War Journal, Bill Roggio, told Fox News Digital. "Numerous al-Qaeda leaders and operatives shelter inside Iran."

Roggio said al-Adel's ties to the Iranian regime and placement inside Iran could make him a "far more dangerous" al-Qaeda leader than his predecessor, but he noted that al-Adel's leadership style was relatively unknown. 

Senior fellow at the American Enterprise Institute (AEI) Michael Rubin, who also spent time embedded with the Taliban before 9/11, echoed Roggio's sentiments and said the news that al-Adel is being housed in Iran "tears the veil off Iran’s extensive relationship with al-Qaeda."

"The idea that Iran and al-Qaeda can’t work across the sectarian divide is naive," he told Fox News Digital. "From an Iranian perspective, Iran is an Islamic power, not just a Shiite one," he added.

The UN also said it suspects al-Qaeda’s second in command, Abu Ikhlas al-Masri, of residing in Afghanistan, which is currently controlled by the Taliban.

The al-Qaeda commander was reportedly captured in 2010 but freed from Bagram prison following the Taliban takeover in 2021, reported the Long War Journal this week.

Price reminded reporters Wednesday that the Taliban has pledged not to allow Afghanistan to be used as a safe haven for terrorist groups or those that would plot against the U.S. or its allies. 

"We are prepared, willing and able to take action ourselves if the Taliban is unable or unwilling to fulfill the commitments that it has made," he said. "I think you saw that perhaps most vividly late last year when the United States took out the then-leader of al-Qaeda, Ayman al-Zawahiri, who was being provided safe haven in Kabul."

At the time, the Taliban claimed it was unaware that al-Zawarhiri had been in Afghanistan. 

Reuters contributed to this report.