Munich on High Alert After New Year’s Eve Terrorism Threat

 BERLIN — Hundreds of police officers remained on alert in Munich on Friday, after a threat of a suicide bombing attack by the Islamic State led the authorities to evacuate two train stations on New Year’s Eve.

The German authorities said on Friday that five to seven suspects may have been involved in the terrorist threat. The two stations, in the city center and in the city’s Pasing district, were both reopened.

Officials defended their decision to close the two transit hubs hours before midnight and to flood the city with heavily armed officers — 550 as of Friday morning, including police officers from other parts of the southern state of Bavaria. They said they had received a “very concrete tip” around 7:40 p.m. from intelligence sources in France and the United States indicating that militants from Iraq and Syria were planning to carry out attacks.

Extra precautions had already been put in place across the Continent for New Year’s Eve celebrations, less than two months after Islamist militants carried out a series of bloody attacks in and near Paris. Festivities were canceled in Brussels, the seat of many European Union institutions, and extra precautions were in place in Austria, France and the Netherlands after warnings from the intelligence service of an unspecified “friendly” country.

Senior security officials in Washington and in European capitals said that American intelligence agencies had played a major role in detecting possible plots in the days leading up to the year-end holidays and in sharing information.

“Last night’s threat was so specific that we couldn’t wait to determine whether it was serious or not, but had to act,” said Joachim Herrmann, the interior minister of Bavaria.

Although the authorities said the intelligence information had included the names of suspects from Iraq, Hubertus Andrä, chief of the Munich police, said on Friday that no one had been arrested and that the authorities were unsure if the suspects were in the country.

“The situation in Europe and in Germany remains serious in the new year,” Thomas de Maizière, the German interior minister, said in a statement on Friday. “Since the attacks in Paris, we have received several hints. Federal and state security services are following up on these indications, including of possible planned attacks.”

Germany has not experienced the sort of attacks that were carried out in Madrid in 2004, London in 2005 and Paris last year, but the authorities in Berlin warn that the country remains a possible target, most notably because of its military presence in Afghanistan.

The German authorities called off the popular Eschborn-to-Frankfurt bike race scheduled for May in response to information about a potential attack, and they arrested a German-Turkish couple who had been storing weapons in their home.

Days after the Paris attacks on Nov. 13, which included an attempted suicide bombing at a soccer match between the German and French national teams, a game in Hanover between Germany and the Netherlands hours was called off hours before kickoff, because of a suspicious package. No arrests were made.

The authorities in Munich said that police reinforcements would be on duty throughout New Year’s Day. They said that identity checks would be carried out, and asks that residents be patient with the increased security measures.

One resident, Oliver Habel, said he had spent New Year’s Eve in a restaurant in the southern part of the city, and only learned about the terrorism scare on Friday morning. “I am very confident in the security measurements in Bavaria, so I am not concerned,” he said.