MADRID — The alert came from an informant who warned of impending suicide attacks on the Barcelona subway.
And because the suspected bombers thought the spy was ready to die with them, officials say, he urged authorities to act fast. The paramilitary Guardia Civil raided mosques and apartments in port neighborhoods housing one of mainland Europe's largest Pakistani communities. A judge jailed 10 suspects. Spain warned that bombers had been dispatched for follow-up attacks in Paris, London, Lisbon and Frankfurt.
More than two weeks later, however, the story seems ambiguous. Investigators found only a trace of explosives. No plot was detected in France, and no arrests have been made in any of the other countries. Leaders of the Pakistani community in Barcelona say they were unfairly targeted.
Some Western investigators believe the alleged plot was one of the most serious threats in Spain since the Madrid train bombings that killed 191 people in 2004. Others, including some Spanish anti-terrorism officials, doubt that an attack was imminent.
But they all agree that the case illustrates a shift in the landscape -- and they are struggling to adjust.
For years, Al Qaeda leaders based in Pakistan almost exclusively targeted Britain, using radicals among the more than 1 million residents of South Asian descent. Those networks have showed greater ability and determination to strike the West than the North African or Middle Eastern groups that have been the main threat to continental Europe.
During the last six months, however, Danish, German and now Spanish authorities have broken up alleged plots linked to the Waziristan region of Pakistan, where investigators have detected an increase in Western recruits at clandestine training compounds. The cases suggest that Al Qaeda and its allies are trying to recruit within a rapidly growing Pakistani immigrant population in continental Europe.
As Britain has toughened border controls, more South Asian immigrants have headed elsewhere in Europe seeking economic opportunity and respite from turmoil at home. Some have arrived legally, but others travel along smuggling routes through the Middle East and Africa.
Although extremists remain a small minority, the presence of militant cells has increased along with the population, anti-terrorism officials say.
