An Islamist mistakenly arrested in Cairo on suspicion of being a senior Al-Qaeda figure has been freed, judicial sources and state media said on Thursday.

Muhamed Makkawi, confused for the senior Qaeda militant known by the nomme de guerre of Seif al-Adel, was arrested at Cairo airport on Thursday, with state media and police announcing they had netted the Al-Qaeda commander.

He was freed on Friday after questioning, judicial sources and the official MENA news agency said.

Makkawi had apparently come back to his native Egypt from Pakistan to clear his name after law enforcement agencies confused him with Adel, who was said to have led Al-Qaeda briefly after Osama bin Laden's death last year.

The FBI offers a reward if up to $5 million Adel, whom it also identifies as Makkawi.

But the picture posted under his name on its Most Wanted list is of another Egyptian, Mohammed Zeidan, analysts and Islamist activists who knew both men say.

Omar Ashour, an expert on Islamist militant groups, said Makkawi had been trying to clear his name for years. Makkawi had settled in Pakistan after fighting the Soviet occupation of neighbouring Afghanistan in the 1980s.

"On the FBI website they have a picture of Zeidan but the biography of Makkawi," said Ashour, a professor at Exeter University.

Ashour said Makkawi had contacted the United Nations High Commissioner for Refugees, before he reached out to a pan-Arab newspaper to clarify his identity.

"There are a few reasons (for confusing the two Egyptians)" Ashour said.

"One of them has to do with the other man's background. Mohammed Zeidan was also in the armed forces. Both come from the (Nile) Delta region."