Other questions concern Rashid Rauf, a Birmingham, England, businessman living in Pakistan. His arrest there caused the suspects here to film a martyrdom video, which in turn triggered the police decision to round up the group last month, the British counter-terrorism official said. Pakistani authorities describe him as a key figure who has confessed to meeting with an Al Qaeda leader about the plot.
British officials, in contrast, say Rauf communicated frequently with the London group, but his role is unclear. One official said Rauf did not appear to be a mastermind. European anti-terrorism officials worry that information from Pakistan tends to be clouded by political manipulation and unsavory tactics.
Rauf confessed after four days of interrogation, which raises the specter that he was tortured, said a European anti-terrorism official with information about the case.
"After four days of interrogation, I think he would say pretty much what they wanted," the European official said. "I am a little bit skeptical."
Although the same problem haunts cooperation with North African and Arab security agents, intelligence from North Africa helped police in Paris detect a major threat developing about a year ago. It emerged from the fury in Iraq, a land of jihad that is revitalizing and reshaping networks such as Algeria's Salafist Group for Call and Combat, known by the French initials GSPC. The GSPC, a longtime Al Qaeda ally, spent the late 1990s embroiled in Algeria's bloody civil conflict. It expanded throughout the Maghreb countries, north into Europe and south into the Sahel region of countries including Mali and Niger. With the advent of war in Iraq, combat-hardened Algerians were a large component of the jihadists flocking to join the insurgency along with inexperienced Europeans, who tended to be thrown into the fray.
"At the start of war there are very radicalized extremists, and it's kind of the era of cannon fodder in which Zarqawi and other organizations absorbed these people and sent them on suicide operations," Bruguiere said. "Later, in 2005, while the situation is degrading in Iraq, some of these people are recuperated by the Zarqawi movement, and groups like it, to be trained for terror operations in Europe."
The Algerian network began working with Zarqawi and others to develop a regionwide version of Al Qaeda that would unite groups in Morocco, Mali, Libya and elsewhere and create "a zone of destabilization" across northern Africa, French and Italian investigators said.
"The strategy changes," a senior Italian police official said. "The GSPC loses its nationalist Algerian focus, embraces the anti-Western ideas of Al Qaeda. They set up new training camps on the border of Algeria and Mali that disappear whenever someone looks for them. And they form a big structure in Syria, in Aleppo and Damascus, that sends some foreign fighters who come to Syria into Iraq, and others back to Europe."
Leaders forged the alliance partly with traveling emissaries and e-mails, including one intercepted by the CIA in late 2004, officials say. But it was also a fluid process that is typical of Islamic extremism and has intensified as Al Qaeda's networks have been damaged and dispersed, they say. The "emirs" set a general strategy guiding the initiatives of the cells, which are often spontaneously formed and largely autonomous.
In exchange for fighters and logistics, Zarqawi and like-minded bosses in the Iraq region decided to provide manpower and training -- in Iraq, Syria, Lebanon -- to help the GSPC attack France, a dire foe because of its support for the Algerian government. The Jordanian began singling out Algeria and France in propaganda statements and terrorist operations.
As Iraq grew increasingly chaotic last year, insurgent chiefs had more wannabe foreign fighters than they could handle, investigators said.
"In 2005, the flow of jihadis to Syria was unmanageable," the senior Italian police official said. "There were too many, and too many were untrained. The structure in Syria decided that they only wanted serious people with combat experience, especially from the Algerian army. The others are sent to Algeria to the camps to train. Because the GSPC wants to hit Europe."
The new alliance produced brazen schemes to bomb targets in France: the Paris subway, the Orly airport, the headquarters of the DST anti-terrorism agency, even a Parisian restaurant frequented by DST agents.
Starting with the capture of a boss in Algeria last September and continuing into the spring, security forces launched periodic raids north and south of the Mediterranean. The operations revealed that new cells inherited projects from dismantled groups and tried again.
The suspects were a cross-section of extremism today. French police arrested accused ringleaders Safe Bourada, 35, and Ouassini Cherifi, 31. Both are from Algerian immigrant families and grew up in tough suburbs of Paris. Both did time on previous terrorism charges.