The latest purported taped message from Osama bin Laden has raised concern among European intelligence and law enforcement officials that their countries are now on his hit list. Security officials are especially worried that the voice on the tape specifically mentions four European countries, Britain, France, Germany and Italy, as potential targets for al-Qaida operatives or associates.

Although some European politicians are wary about sowing panic and have played down fears of an imminent terrorist attack, intelligence and counter-terrorism officials appear to be willing to override their political masters and have openly warned that the threat against Europe from al-Qaida is greater today than it has ever been.

France's leading anti-terrorism magistrate, Jean-Louis Bruguiere, said Thursday that people in Europe, and especially in France, need to know that the risk of an attack is real and high.

And even before the purported bin Laden tape was issued Tuesday, Germany's intelligence chief, August Hanning, said that Germans have to be ready for what he described as a new attack of a much larger dimension.

Independent counter-terrorism experts say these officials are conscious of the need to balance the risks of raising public fears with the risks of under-preparedness. Jonathan Stevenson, an expert at London's International Institute of Strategic Studies, says the Europeans have followed the lead of their colleagues in the United States, whose warnings have not produced undue panic, and may even have created more awareness and sensitivity to terrorist threats among Americans.

"Basically, the warning that was issued by bin Laden, and the European response to it, suggests that the Europeans are taking on board the observations of a number of experts and a number of U.S. government officials that al-Qaida has, in fact, reconstituted in the wake of the Afghanistan campaign, and is now really a more dispersed, decentralized, a more virtual organization, if you will, and, in a certain way, one that is much more difficult to defeat," he said.

Although several European countries have cracked down hard on alleged terrorist cells in the 14 months since the September 11, 2001 attacks against the United States, the warnings in recent days have made clear that such cells and the networks that often link them together are still alive and well in Europe.

Intelligence and counter-terrorism officials generally agree that, even with stepped-up measures against terrorists, it is impossible for open, democratic governments, like those in Europe, to create absolute security.

Mr. Stevenson says it is very difficult to ascertain what the time interval is going to be between a warning such as the one issued on the purported bin Laden tape and the terrorist attack itself.

"When bin Laden issues a warning like this, it certainly could be construed as an inspiration to a terrorist attack by a local al-Qaida affiliate," he said. "And, you know, that connects with the observation that, increasingly, al-Qaida will rely on local talent, so to speak, since it no longer really has a central base in some place like Afghanistan. That's not to say that they won't use sort of mid-level coordinators, who come from outside the locale of the given terrorist attack. But it seems probable that they will tend to relinquish the initiative to a degree, at least to operational specifics, to local groups such as Jemaah Islamiyah in Indonesia."

Jemaah Islamiyah has been linked to the bombing on the Indonesian island of Bali last month that killed more than 180 people.

Mr. Stevenson says there were vague warnings and dubious intelligence that something was going to happen in Southeast Asia before that attack. But he says, the information was so general that it was very difficult to act on.

European intelligence officials are scrambling to make sure that does not happen on their turf. One German official says he and his colleagues are at a stage where they have some facts, but are still lacking concrete details about the next attack.