The killing of Osama bin Laden is undoubtedly a triumph for the administration of the US president Barack Obama. But as the president himself has recognised, it does not mean the end of al Qa'eda, which will remain among the most serious security threats to the United States and its allies.
Nearly a decade after the September 11 attacks on the United States, al Qa'eda has transformed itself from a centralised group to a brand name used by assorted jihadist movements across the globe. The organisation founded by bin Laden in the 1980s has morphed into small, localised cells and affiliated groups that do not necessarily take orders from the old leadership. But it is clear they have been inspired, if not specifically directed, by bin Laden.
Al Qa'eda and its offshoots have carried out smaller-scale attacks including the March 2004 bombings of four commuter trains in Madrid and the July 2005 transit bombings in London. Today, perhaps the most dangerous affiliate is al Qa'eda in the Arabian Peninsula, which has claimed responsibility for a series of near-miss attacks on the United States, including the attempted bombing of a Detroit-bound airliner on Christmas Day 2009.
One of the group's leaders is Anwar al Awlaki, an American-born cleric who now lives in hiding in Yemen. His stature within al Qa'eda is likely to rise as militants seek other charismatic figures to pick up bin Laden's mantle.
In announcing bin Laden's death on Sunday evening, Mr Obama warned that al Qa'eda remains active and the US could face retaliation. "There is no doubt that al Qa'eda will continue to pursue attacks against us," Mr Obama said. "We must and we will remain vigilant at home and abroad."