Al Qaeda's new leader Ayman al-Zawahri
Al Qaeda's new leader Ayman al-Zawahri is shown in this undated file photo.

The long-serving second-in-command of al-Qaeda, Ayman al-Zawahiri, has been appointed its head following the death of Osama Bin Laden, the militant organisation said in a statement.

Al-Qaida gave no details about the selection process for bin Laden's successor but said that it was the best tribute to the memory of its 'martyrs'.

Mr Zawahiri is Egyptian born and thought to be in his late-50s, while he currently a fugitive and his whereabouts are unknown. He first met bin Laden in the mid-1980s when both were in Pakistan to support guerrillas fighting the Soviets in Afghanistan.

While Mr Zawaihri is a well-known figure in the Islamic world, many still cast doubts on his ability to command the following that bin Laden enjoyed among jihadists not only in the Gulf States but across the Middle East and Africa.

While he was always the likely choice to take over from bin Laden, the Egyptian terrorit does not have the charisma or legendary status of Al Qaeda's founder, say jihadist experts.

As the head of the terrorist organisation has been confirmed, analysts are now looking to see who will be appointed Zawahri's number two, believing this will be a more telling indication of what the network's nature and priorities will be.

Mr Zawahiri is the son of an upper-middle-class Egyptian family of doctors and scholars. His father was a pharmacology professor at Cairo University's medical school and his grandfather was the grand imam of Al-Azhar University, a centre of religious study with a worldwide reputation and his family was said to be rather conservative.

He originally was a quiet student but appear to have started down the road to radicalism after the Israeli's defeat of several Arab armies in 1967. Aged 14 he joined the Muslim Brotherhood and went on to become a member of Islamic Jihad. At the same time he was studying medicine and eventually qualified as a surgeon, but increasingly his time was taken up by radicalism.

By the time of the assassination of President Sadat in 1981 he was a senior leader in Islamic Jihad. He was rounded up in the resulting crackdown, jailed for three years, and severely tortured whilst in prison.

Upon release he struggled to find work in medicine due to his connections with Islamic Jihad and fled to Afghanistan to join the thousands of Arab fighters who had gone to fight the Soviets.

There he met Bin Laden and eventually the two men merged their different Mujahidin groups to form 'The World Islamic Front for Jihad Against Jews And Crusaders', which became known as Al Qaeda .

Zawahiri was also wanted in the US even before the 2001 attacks on New York's World Trade Centre and the Pentagon, which killed more than 3,000. He was indicted in absentia in 1999 for the August 1998 bombings of US embassies in Tanzania and Kenya that killed 224 people, and was also considered the mastermind.

In a video message posted on the internet on June 8, Mr Zawahri said al Qaeda would continue to fight.

"The Sheikh (bin Laden) has departed, may God have mercy on him, to his God as a martyr, and we must continue on his path of jihad to expel the invaders from the land of Muslims and to purify it from injustice," Mr Zawahri said.

"Today and thanks be to God, America is not facing an individual or a group ... but a rebelling nation which has awoken from its sleep in a jihadist renaissance challenging it wherever it is."

However the appointment of Zawahiri six weeks after the death of Osama bin Laden raises several questions. His appointment at the head of the organisation did not come as a surprise, so it would be intriguing to know why it took Al Qaeda's leaders so long to officially put him as the head of the movement.

While Zawahri is well known he is not necessarily well liked and certainly does not score unanimity even among Al Qaeda members. His credibility as a strong leader of Al-Qaeda was also further diminished when a Saudi Newspaper accused him of leading the Americans to Bin laden and thus causing his death.

The paper insists that Zawahri always wanted to be the organisation main chief and that his relationship with Bin Laden became strained in the last decade.

At the time, the newspaper wrote "Al-Qaeda chief Osama bin Laden was betrayed by his deputy Ayman al-Zawahiri who led US forces to his hideout as the two were involved in an intense power struggle"

"The two top al-Qaeda men had differences and the courier who led US forces to bin Laden was working and had more loyalties for Zawahiri," the newspaper also reported.

Whether or not the accusations are true, the fact that Zawahiri was so publicly accused of betraying the emblematic figure of the organisation illustrates the limitations of his ideological influence.

Moreover, there are also allegations that Al-Qaeda is now a deeply fractured organisation where factions struggle to acquire power. Many accused Zawahiri, of trying to take control of the organisation with the help of the Egyptian faction when Bin Laden was taken ill in 2004.

While intelligence services around the world remain conscious of the continuing threat from Al Qaeda and now that Zawahiri leads Al Qaeda he will want to make his mark and "continue the fight".

However, over the last ten years, at least a third of the higher echelons of the leadership has been killed or captured.

This has inevitably led to a change of structure inside the organization and a presents a challenge for the new leader. While Al Qaeda used to be hierarchical, with affiliated groups coming to central command for funding and approval for terrorist plots, since the war on terror, the structure has changed. There are now many more 'franchise' Al Qaeda groups who have their own structures and leadership and without Bin Laden they are far less likely to listen to orders or even advice from Zawahiri.