Updated at 10:32 a.m. ET: CAIRO, Egypt – A man arrested in Cairo International Airport on Wednesday on suspicion of being a senior al-Qaida leader appeared to be the victim of mistaken identity, U.S. officials said.

Egyptian security sources originally told NBC News and other media organizations that the man arrested was Mohammed Ibrahim Makkawi, who is also known as Saif al-Adel. Al-Adel is thought to have been put in charge of the tactical planning of al-Qaida attacks since the death of Osama bin Laden in May.

Speaking to The Associated Press, two U.S. officials later said that the arrested man appeared to have been mistaken for the wanted al-Qaida leader. The officials spoke on condition of anonymity to discuss intelligence information that has not been publicly released.

A National Security Council official also told NBC News that the situation appeared to be a case of mistaken identity.

The FBI said it was still sorting out details of the case.

"We are aware that an individual has been taken into custody and every effort is being made by the U.S. government to verify the identity of the person in custody," said William Carter, a spokesman at FBI headquarters.

Embassy bombings
The FBI has listed Mohammed Ibrahim Makkawi on its most-wanted list as an alias for the senior al-Qaida leader known as Saif al-Adel, an Egyptian who has been indicted by the United States for an alleged role in the Aug. 7, 1998 bombings of U.S. embassies in Tanzania and Kenya that killed 224 people. He also was linked to the 2002 killing of Wall Street Journal reporter Daniel Pearl.

Nazar Ghorab, a prominent Egyptian defense lawyer, told NBC News the man arrested at the airport was not al-Adel. Ghorab said the detained suspect was a sometime member of several Islamist militant groups who was nowhere as senior as al-Adel.

Ghorab was one of al-Adel's lawyers in Egypt and represented him and other prominent Islamist militant leaders including Mohammed al-Zawahiri, the brother of current al-Qaida leader Ayman al Zawahiri.

NBC News and others originally cited the FBI which identified "Muhamad Ibrahim Makkawi" as a high-ranking member of the terrorist group. 

Makkawi was arrested after traveling to Egypt from Pakistan via the United Arab Emirates, sources told NBC News. He was detained upon arrival and handed over to Egyptian intelligence officials, NBC News said.

The FBI describes al-Adel as "a high-ranking member of the al-Qaida organization" and the State Department has offered a reward of up to $5 million for information leading to his arrest or conviction.

'Lies'
Speaking to reporters at the airport, Makkawi said he al-Adel and that he had nothing to do with the terror group since 1989.

"I am not the wanted Saif al-Adel," Makkawi 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.

Makkawi gave his birth date as Dec. 17, 1954. The FBI says Saif al-Adel was born in the 1960s.

Wearing a gray Arab robe and a jacket, Makkawi looked nothing like the man in the photograph distributed by the FBI as that of Saif al-Adel's. Makkawi has receding silver hair and wears glasses.

Makkawi said that Saif al-Adel's real name was Mohammed Salah Zidan. Montasser el-Zayat, a lawyer who represented Makkawi in Egypt, also told the AP last year that al-Adel's real name was Mohammed Salah Zidan. Al-Adel's FBI profile was posted in October 2001 when the FBI "Most Wanted Terrorist" list was created -- just a month after the Sept. 11, 2001 attacks. The name "Mohammed Salah Zidan" is not mentioned in the FBI profile.

"I challenge any security agency to prove that I am Said al-Adel, who is a different person whose name is Mohammed Salah Zidan," said Makkawi.

A senior Egyptian security official involved in the case supported Makkawi's assertion of innocence. The official said Makkawi was a former army officer who left Egypt in the 1980s to join the fight against Russian forces in Afghanistan.

The official said Makkawi was wanted for questioning in Egypt in a case dating back to 1994 that involves the activities of a militant  group, whose members fought the government of ousted president Hosni Mubarak in an insurgency in the early 1990s.

The officials spoke on condition of anonymity because they were not authorized to speak to the media.

NBC News' Ayman Mohyeldin, Charlene Gubash, Kristen Welker, Robert Windrem, msnbc.com staff and The Associated Press contributed to this report.

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