A senior al-Qaeda commander was initially reported to have been arrested in Egypt on Wednesday before doubts emerged about his identity.
Egyptian state media said that Mohammed Ibrahim Makkawi was arrested at Cairo International Airport, and added that he was also the al-Qaeda leader Saif al-Adel ('the sword of justice').
Officials said he was travelling on an Emirates Airline flight from Pakistan via Dubai, using travel documents issued by the Egyptian embassy.
Adel is wanted for taking part in both the 1998 bombings of US embassies in Kenya and Tanzania, and the 2001 attacks on New York and Washington.
The FBI 'Most Wanted' lists Adel and Makkawi as the same man, and reports he is roughly 52 years old.
He was once Osama Bin Laden's security chief and remains a member of the terrorist group.
The US has offered a reward of $5m for information leading to Adel's capture or death.
As such state media trumpeted the arrest made on Wednesday as a great achievement.
But within a couple of hours of the man's arrest other reports emerged that claimed the authorities had got the wrong man.
"I am not the wanted Saif al-Adel," Makkawi he told reporters, said the Associated Press. "What has been said about me is lies. I never took part in actions against people or installations."
According to a lawyer who works with militant Jihadist groups the two identities are not the same.
He says that Makkawi was a former Egyptian officer who had not ben connected to al-Qaeda for many years.
It was later claimed that Egyptian security had accepted while the man was wanted for terrorism offences, he was not Saif al-Adel.
Despite the case of apparently mistaken identity, Egyptian news agency Mena continued to insist that Saif al-Adel was captured, and had been given to the Higher State Security Prosecution for interrogation.