There has been a wide range of reaction from around the world in response to the news that Osama bin Laden has been killed and the impact his death will have.
Experts from the Centre of Defence Studies (CDS) at King's College London said al Qaida will "undoubtedly" recover and strike back in retaliation for his death.
While bin Laden's death will come as a "major blow" for the terrorist organisation, the American "triumph" could lead to serious reprisals, they warned.
John Gearson, reader in terrorism studies and director of the CDS, said: "I think the significance of what has happened cannot really be overstated. I would expect embassies and military bases around the world to be on high alert for some time."
Former British Army colonel Richard Kemp, commander of British forces in Afghanistan in 2003, echoed his fears, suggesting the Taliban could now look to bin Laden's deputy, Ayman al Zawahiri, for leadership. He told the BBC: "I think this is not the end of al Qaida by any means."
Meanwhile, Afghan president Hamid Karzai said the death of the terrorist mastermind in Pakistan proves that the fight against terrorists should be focused on the neighbouring country. He added that he hoped bin Laden's death will mean the end of terrorism, adding that he received his due punishment.
But Pakistan's foreign ministry said the death of bin Laden shows the resolve of his country and the world to fight terrorism.
Also on Monday, former prime minister Tony Blair, whose premiership was in many ways shaped by the September 11 and July 7 atrocities, expressed his "heartfelt gratitude" to Mr Obama and those who carried out the military operation which killed bin Laden.
In a statement released by his office, he said the operation showed that "those who commit acts of terror against the innocent will be brought to justice, however long it takes".