Zawahiri has taken command of Al-Qaeda after the killing of Osama Bin Laden, a website said on Thursday. The move was widely expected following his long years as second-in-command. Bin Laden's lieutenant and the brains behind much of Al-Qaeda's strategy, Zawahiri vowed this month to press ahead with Al-Qaeda's campaign against the United States and its allies. “The general leadership of Al-Qaeda group, after the completion of consultation, announces that Sheikh Dr. Ayman Zawahiri, may God give him success, has assumed responsibility for command of the group,” the website Ansar Al-Mujahideen said in a statement posted on a website. The bespectacled Zawahiri had been seen as Bin Laden's most likely successor after the man held responsible for the Sept. 11, 2001 attacks in New York and Washington was shot dead by US commandos in Pakistan. His whereabouts are unknown, although he has long been thought to be hiding along the border between Afghanistan and Pakistan. The United States is offering a $25 million reward for any information leading to his capture or conviction. Former US intelligence officer Robert Ayers said Zawahiri was “a man lacking in charisma, a pale shadow of Bin Laden”. “He's a grey bureaucrat, not a leader who can energize and rally the troops. The only thing his promotion will accomplish is to elevate his priority as a target for the US.” Sajjan Gohel of Asia-Pacific Foundation security consultants said Zawahiri had been in practical charge of Al-Qaeda for many years, but lacked Bin Laden's presence and his “ability to unite the different Arab factions within the group”. Fawaz Gerges, a Middle East expert at the London School of Economics, said Al-Qaeda's militants in South Asia were “on the run”, its leaders were deep in hiding, and a new leader would do little to help it reverse their fortunes. As for its branches in other parts of the world, they were “pitted in a fierce local struggle for survival... and are unable to coordinate their actions with the parent organization.” Henry Wilkinson of Janusian consultants said Al-Qaeda's ability to attack had been fading since the 9/11 attacks. “Al-Qaeda's main achievement has been to have survived,” he said. Others see in Zawahiri a more accomplished figure. London-based journalist Abdel-Bari Atwan, who interviewed Bin Laden in 1996, said Zawahiri was the “operational brains” behind Al-Qaeda and was respected in part because, he said, he had been Bin Laden's chosen deputy. Believed to be in his late 50s, Zawahiri met Bin Laden in the mid-1980s when both were in Pakistan to support guerrillas fighting the Soviets in Afghanistan. Born to an upper-class Cairo family, Zawahiri trained as a doctor and surgeon. In a video message posted on the internet on June 8, Zawahiri said Al-Qaeda would continue to fight. He called this year's Arab uprisings a disaster for Washington because, he said, they would remove Arab leaders who were the “agents of America”. He also pledged allegiance to the leader of the Afghan Taliban, Mullah Omar, calling him “Emir of the Believers”. US vows action The United States will seek to hunt down and kill Ayman Al-Zawahiri just as it did his predecessor Osama Bin Laden, the top US military officer said Thursday. “There is not a surprise from my perspective that he's moved into that position,” Admiral Mike Mullen, the chairman of the Joint Chiefs of Staff, told journalists after the Egyptian leader was named the new Al-Qaeda chief. “He and his organization are still threatening us, and as we did both seek to capture and kill – and succeed in killing – Bin Laden, we certainly will do the same thing with Zawahiri.” — AgenciesKey facts about Ayman Al-Zawahiri He is described as the chief organizer of Al-Qaeda and was Bin Laden's closest mentor. Zawahiri and Bin Laden met in the mid-1980s when both were in the Pakistani city of Peshawar to support guerrillas fighting the Soviets in Afghanistan. Born in 1951 to a prominent Cairo family, Zawahiri was the son of a pharmacology professor and grandson of the grand imam of Al-Azhar, one of the most important mosques in the Arab world. He graduated from Egypt's most prestigious medical school in 1974. When the militant Egyptian Islamic Jihad was founded in 1973, he joined. When members posed as soldiers and assassinated president Anwar Sadat in 1981, he was among 301 people arrested. Zawahiri has broadcast dozens of messages since the Sept. 11 attacks on the United States in 2001. In April, he urged Muslims to fight NATO and American forces in Libya. In Jan. 2006 Zawahiri called US president George W. Bush a “butcher” in a video tape, saying a US airstrike targeting him had killed only innocent people. Earlier this month Zawahiri released a new video recording following the death of Bin Laden in May, vowing to press ahead with the group's campaign against the United States and its allies. __