Al Qaeda has splintered off into countless autonomous Islamist cells, creating a tricky moving target for law enforcement, Germany's domestic intelligence service chief said Thursday.

"They are apparently no longer in a position to plan attacks or lead operations like we saw on Sept. 11," Heinz Fromm said in an interview with AFP news service on the eve of the anniversary of the London bombings.

As in the attacks that rocked the British capital, the danger is now more likely to originate from small groups of radicalized local Islamists, he said.

"Five people, maybe even fewer, are enough to plan an attack," he said.

A year ago, four British bombers killed 52 people and maimed about 700 more on the capital's transport network in the July 7 attacks of last year in an atrocity that awoke the nation to the reality of home-grown Islamist suicide attacks.

An ideology

Fromm said European security officers faced a constant battle monitoring such groups and keeping them under control.

"There is no operational headquarters for al Qaeda somewhere in the mountains --the groups now operate locally," he said. "Today it is more an ideology -- the foundations of holy war -- that is propagated by Osama bin Laden and other leaders."

He said young Muslims drew inspiration from images of battles and attacks in Iraq on the Internet or the messages sent by bin Laden and al Qaeda No. 2, Ayman al Zawahiri.

"These people think about how they could contribute to global jihad," he said, adding that some go to Iraq to mount suicide bombings while others focus on Europe as a potential target.

Fromm said European security sources faced the dual challenge of stopping the insurgency in Iraq from growing due to a flow of volunteers from Europe, and stopping militants returning from Iraq from plotting attacks in Europe.

"Those extremists who have been in Iraq enjoy great respect among young people," he said, adding that they had the potential to become cell leaders.

Fight extremism, Blair says

As London marks the first anniversary of the world peacetime attack on London, British Prime Minister Tony Blair urged British Muslims to step up fight against Islamist extremism after a poll showed that more than one in 10 of them think the London bombers were martyrs.

Blair insisted there was "no doubt" that a home-grown terror threat to Britain remained and that Islamic extremism in Britain could not be defeated by his government's efforts alone and stressed that moderate Muslims needed to speak up more.

"There is no doubt there are people, there are groups that we believe are engaged in planning this kind of activity," Blair told parliament. "I think the roots of this extremism lie in the attitudes and ideas as much as organization. I don't think there is an answer to this terrorism that is simply about police work or security measures. You cannot defeat this extremism through what a government does -- you can only defeat it within a community."

Britain's Muslim community numbers 1.65 million people, 2.8 percent of the population.

Stepped up measures

Meanwhile, Peter Clarke, head of the anti-terrorist branch at London's Metropolitan Police, said this week that police were investigating an unprecedented 70 terrorist-related cases at home and in the rest of the world, warning that the information being uncovered was "very sinister."

He also revealed that officers had stopped three and probably four attacks since the July 7 bombings.

"The level of counter-terrorist investigations has intensified during the past 12 months," Clarke told reporters. "There has been an unrelenting demand for intelligence to be investigated and operations conducted to arrest suspects or disrupt terrorist activity when judged to be appropriate."

Sixty people are currently awaiting trial in Britain for crimes linked to terrorism, the officer said.

"This is unprecedented and the flow of new cases shows no sign of abating -- if anything it is accelerating," he warned.

Two alarming features were emerging from the arrests: firstly, that the majority related to British citizens wanting to commit offences against their fellow countrymen and secondly, the young age of some of the suspects.

Clarke attributed the radicalization of young men to a range of factors including a perceived sense of injustice, a sense of alienation and the influence of extremist clerics.

Continuing manhunt

A year later, police are still trying to reconstruct the events leading up to the coordinated attacks, hoping to identify anyone who might have had prior knowledge of the suicide blasts.

Clarke said it was still possible that criminal charges could be brought even though London's largest investigation in history has still yet to see anyone charges in connection with the attacks.

"We need to know who else, apart from the bombers, knew what they were planning," he said. "Did anyone encourage them? Did anyone help them with money? Accommodation? Or expertise in bomb making?"

And questions still remain about how and why Khan, Tanweer, Hasib Hussain, 18, and Germaine Lindsay, 19 -- four British Muslims with fairly ordinary backgrounds -- became suicide bombers.