Analysis: Al-Qaeda has been disrupted but not disabled, and local groups are nowmore likely to carry out attacks, write Roula Khalaf and Stephen Fidler
The centre of the struggle against violent Muslim extremism has been firmly in Iraq since the US-led invasion in 2003.
But yesterday's co-ordinated attacks against the London transport system is a stark reminder that the war against Islamist terrorism has more than one battlefield.
Although there was no confirmed claim of responsibility or confirmation of the identity of the culprits, most security specialists assumed the attacks were by Islamist extremists.
Since the attacks in New York and Washington in September 2001, military action by the US-led coalition in Afghanistan is widely assumed to have disrupted severely - though not disabled - the ability of Osama bin Laden and his lieutenants to command and control terrorist organisations around the world.
This central core of al-Qaeda remains able to inspire recruits, to provide ideological motivation and possibly to regroup.
But its disruption has made what was already a loose network of like-minded groups even more diffuse and harder to target.
Attacks are thus more likely to be planned and carried out by local groups.
"Al-Qaeda is a strategy, an umbrella, not a pyramid structure," said Abdelbari Atwan, editor of the London-based al-Quds al-Arabi newspaper and an expert on the network.
In a similar pattern to their counterparts across Europe, which is home to 20 million Muslims, UK police and security services have been focusing increasingly on the perceived threat posed by indigenous radicalised Muslims.
This small minority of youth, often from second- or third-generation immigrant families, are said to be motivated by a feeling of disaffection with the society in which they have grown up and the perceived maltreatment of Muslims at home and in the Middle East by Western powers.
The various groups, says a senior US government terrorism specialist, "may be united only by something so simple and amorphous as ideology".
Fundamentalist ideologues seek the replacement of secular governments, at least initially in the Middle East, by a caliphate or religiously guided administration.
Europeans have joined the hundreds of radical jihadis who have been streaming into Iraq since the invasion, and it is feared that some of these may be returning to Europe, trained in violent tactics of urban terrorism.
Yet at first sight, the attacks in London resembled most the rush-hour attacks in March 2004 in Madrid which appeared designed to maximise disruption and encourage popular panic.
The attacks generated further impact by their timing as the G8 leaders gathered in Scotland.
"They figured that the best way to hit at the economy is to paralyse the transport system," said Saad al-Faguih, a London-based Saudi Islamist dissident who keeps a close watch on al-Qaeda.
"They needed to prove that, with all the vigilance over the G8 summit, the UK was still exposed."
Messages of congratulations were exchanged yesterday on chat rooms of websites used by jihadis after a previously unknown group calling itself the "Secret Organisation of the al-Qaeda Jihad in Europe" posted a statement claiming responsibility for the blasts "in revenge of the massacres that Britain is committing in Iraq and Afghanistan".
The group threatened Denmark and Italy with similar "punishment" unless they withdrew troops from Iraq.
The statement said the UK had been repeatedly warned.
"And here we are fulfilling our promise and implementing a blessed military invasion in the UK following strong efforts by our mujahideen and heroes, efforts that took a long time to plan to ensure success."
The UK, the closest ally of Washington, has been high on the list of targets for the network.
Until yesterday, however, the only attacks on British targets outside Iraq were the 2003 bombings at the British consulate and HSBC bank in Istanbul.