Osama bin Laden (L) sits with his adviser and purported successor Ayman al-Zawahiri, an Egyptian linked to the al-Qaida network, during an interview with Pakistani journalist Hamid Mir (not pictured) in an image supplied by the respected Dawn newspaper Nov 10, 2001. [Photo/Agencies]

ISLAMABAD - Egyptian-born doctor and surgeon Ayman al-Zawahri is al-Qaida's second-in-command expected to succeed Osama bin Laden following his killing in a firefight with US forces in Pakistan. Live report

Zawahri has been the brains behind bin Laden and his al-Qaida network, and at times its most public face, repeatedly denouncing the United States and its allies in video messages.

In the latest monitored by the SITE Intelligence Group last month, he urged Muslims to fight NATO and American forces in Libya.

"I want to direct the attention of our Muslim brothers in Libya, Tunisia, Algeria, and the rest of the Muslim countries, that if the Americans and the NATO forces enter Libya then their neighbours in Egypt and Tunisia and Algeria and the rest of the Muslim countries should rise up and fight both the mercenaries of Gaddafi and the rest of NATO," Zawahri said.

Born into an upper-class family of scholars and doctors in an upscale Cairo neighbourhood, the cerebral Egyptian in his late-50s is second after bin Laden on the FBI "most wanted terrorists" list.

Both bin laden and Zawahiri eluded capture when US-led forces toppled Afghanistan's Taliban government in late 2001 after al-Qaida's Sept. 11 attacks on US cities.

But on Sunday bin Laden was killed in a firefight with US forces and his body was recovered, US President Barack Obama said. There was no word on Zawahri.

Bespectacled, with grey hair and a grey beard, Zawahri won prominence in Nov. 2008, when he attacked then US President-elect Obama as a "house Negro," a racially-charged term used by 1960s black American Muslim leader Malcolm X to describe black slaves loyal to white masters.

In a subsequent video, in Sept 2009, Zawahri returned to the attack on Obama, saying he was no different from his predecessor George W. Bush.

"America has come with a new deceptive face ... It plants the same dagger as Bush and his predecessors did. Obama has resorted to the policies of his predecessors in lying and selling illusions," said Zawahri, clad in white robe and turban.

Like bin Laden, Zawahri has long been thought to be hiding along the rugged Afghan-Pakistan border. The last video of Zawahri and bin Laden together was broadcast by al Jazeera on Sept 10, 2003. It showed them walking in mountains, calling for jihad and praising the Sept 11 hijackers.