An Egyptian named by the United States as one of Al Qaeda's top figures has been arrested in Cairo, but he has denied the link and says it was a case of mistaken identity.

Security and airport officials say Saif al-Adel was arrested on his arrival Wednesday from Pakistan and was taken for questioning.

U.S officials later said they do not believe that the man arrested is the long-sought senior leader.

A U.S. national security official said Wednesday the arrest appeared to be a case of mistaken identity, but that the U.S. was working with Egyptian officials to be sure.

William Carter, an FBI spokesman, said that "every effort is being made by the U.S. government to verify the identity of the person in custody."

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Speaking to reporters at the airport, al-Adel said he was not the senior Al Qaeda leader and that he had nothing to do with the terror group since 1989.

"I am not the wanted Saif al-Adel," the man told reporters. "What has been said about me is lies. I never took part in actions against people or installations."

"I decided to come to Egypt to live in peace and because I am certain of my innocence," he said.

The U.S. has listed the name Mohammed Ibrahim Makkawi as the real name of Saif al-Adel, a pseudonym that means "sword of justice." But former militants who know both men have previously said they are two different people and the U.S. identification is incorrect.

Al-Adel, a former Egyptian special forces officer, was believed to have taken over Al Qaeda’s leadership after the death of Usama bin Laden and arrived in Cairo on a flight from Pakistan that had a layover in Dubai, the AFP reported. He was taken into custody after handing over his travel documents.

Al-Adel has been on the FBI’s “Most Wanted Terrorists” list, wanted over the 1998 bombings of the U.S. embassies in Dar es Salaam, Tanzania and Nairobi, the report said. He was also reportedly linked to the 2002 killing of Daniel Pearl, the Wall Street Journal reporter.

After the U.S.-led invasion of Afghanistan following the 9/11 attacks, he fled to Iran, where he was reportedly held under house arrest, though it is believed he continued to be active and in recent years he was reportedly allowed to make trips to Pakistan.

Noman Benotman, a Libyan who was once a member of a jihadist group linked to Al Qaeda, says the man arrested is actually Makkawi and is not al-Adel.

Benotman, now an analyst at the London-based Quilliam Foundation, says he has met both Makkawi and al-Adel.

Benotman, who said he has spoken to security officials in Egypt, said Makkawi flew to Egypt "purposely to clear his name as many former jihadists have been released since all of the political changes in Egypt."

FoxNews.com reported earlier this month that al-Adel, thought to be around 50 years old, recently left Iran where he spent years "under house arrest" with four other members of al Qaeda, following the US-led invasion of Afghanistan in 2001. Iran did not acknowledge their detention.

Newscore and the Associated Press contributed to this report.