Senior al-Qaeda operative Seif al-Adel, who was reported to have briefly taken over the militant network's leadership after Osama bin Laden's death, has been arrested at Cairo airport, security officials say.
The officials did not say why the Egyptian militant, who is on the FBI's most wanted list with a reward of up to $US5 million ($A4.66 million) for his capture, flew in to Cairo.
State television also reported his arrest.
An airport official said Seif al-Adel, also known as Muhamad Ibrahim Makkawi and Ibrahim Madani, arrived on an Emirates flight from Pakistan with a stop over in Dubai.
Security officials said the militant, a former Egyptian special forces officer, was arrested after presenting a travel document at customs and taken into custody by the National Security apparatus.
They said he was wanted by the powerful security agency but did not detail the accusations against him.
On its website, the US Federal Bureau of Investigation says Adel has been indicted for alleged involvement in the 1998 bombings of US embassies in Kenya and Tanzania.
Following Bin Laden's death at the hands of US special forces in May last year, Adel was reported to have taken over the militant network before the appointment of another Egyptian, Bin Laden's longtime deputy Ayman al-Zawahiri.