The Foreign Ministry in Tokyo urged Japanese citizens to be cautious when using public transport or visiting popular tourist sites — issuing another blow to Europe’s tourism industry, which is just starting to recover from the global financial crisis.

European authorities — especially in Britain, France and Germany — tightened efforts to keep the public safe in the wake of warnings by officials that the terrorism threat is high and extra vigilance is warranted.

Last week, a Pakistani intelligence official said eight Germans and two British brothers were at the heart of an al-Qaida-linked terror plot against European cities, but the plan was still in its early stages, with the suspects calling acquaintances in Europe to plan logistics. The official said the suspects were hiding in North Waziristan, a Pakistani tribal region where militancy is rife and where the U.S. has increased its drone-fired missile strikes in recent weeks.

Security officials say terrorists may be plotting attacks in Europe with assault weapons on public places, similar to the deadly 2008 shooting spree in Mumbai, India. European officials have provided no details about specific targets.

Former U.S. Homeland Security Secretary Michael Chertoff urged Americans in Europe to take commonsense precautions, such as knowing where they are in a city and identifying an exit at major tourist sites.

"Don’t walk around with the American flag on your back," Chertoff, who headed the agency during the Bush administration, told ABC’s "Good Morning America." ”(Consider) where would you take shelter if something happened."

On Monday, French police arrested a 53-year-old man suspected of links to a bomb threats including one Friday at a Paris railway hub, an official with knowledge of the investigation said on condition of anonymity. The suspect, who was not identified, was detained southwest of the capital for possible links to a phone-in threat at the Saint-Lazare train station.

French authorities recorded nine bomb alerts in the capital in September, including two at the Eiffel Tower — a threefold increase from a year earlier. No explosives were found.

The U.S. State Department alert Sunday advised the hundreds of thousands of American citizens living or traveling in Europe to take more precaution about their personal security. The British Foreign Office warned travelers to France and Germany that the terror threat in the countries was high.

Western nations are aligned in their estimation of the threat, a French official said.

"These American recommendations are line with the recommendations that we have made on our own territory," said Foreign Ministry spokesman Bernard Valero, pointing to France’s "red" terror alert status — the second-highest in the French warning system.

"All countries concerned have a convergent analysis of the high level of threat in Europe," Valero said.

In Berlin, Interior Ministry spokesman Michael Paris said German authorities were taking the latest travel warnings "very seriously," but that there were no indications of an imminent terror threat.

Neither France or Germany has raised its terror alert level recently.

Business travelers and tourists arriving Monday at Paris’ Charles de Gaulle airport from the United States said they were aware of the new warnings but weren’t changing their plans.

"I’m very happy to be here in France. I think we’re very safe, and I trust the French government to keep us safe," said James O’Connell, a 59-year-old from Pittsburgh, arriving in Paris for a 7-day vacation.

Karen Bilh, a 39-year-old traveler, arrived in Paris from Cincinnati.

"We’ll pay extra caution and if there’s terror threats, we’ll listen to police in the area. We’re excited about the trip," she said.

Travelers taking the Eurostar trains between London and Paris were similarly determined not to let the warnings disrupt their plans.

Jennifer D’Antoni, who owns a retail clothing store in Britain, was in Paris to celebrate her birthday.

"I had a wonderful time and I’ll come back again. In fact, I wish I was here for another day because I didn’t get to see everything. We are just going to be a bit more cautious getting on the train," she said.

Yet Germans — authorities and citizens alike — were not convinced of the need for concern.

"I think it is quite exaggerated," said Marian Sutholt, 25, of Berlin. "If you worry all the time, you actually live up exactly to what the terrorists want. So you should take things as they come and not worry too much. Hopefully nothing will happen."

But John Gooley, a tourist from Portland, Oregon, was more cautious.

"Berlin is an amazing city, its a beautiful city, but I’d probably recommend staying in smaller cities," he said Monday. "I am still happy to travel all throughout Europe, but for right now I might avoid Paris, Berlin, London."

At Washington’s Dulles airport, Jennifer Mackey, an American traveling to Germany, said: "I don’t think we should be in a fear-based society."

"I think if we stop traveling, the so-called quote, unquote ‘enemy’ has won," she said. "I think life has to carry on."

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Associated Press writer Shino Yuasa in Tokyo and AP Television News reporter Nicolas Garriga in Paris and Dorothee Thiesing and Juergen Baetz in Berlin contributed to this report.