Germany received a tip hours before midnight that named militants from Iraq and Syria were planning attacks in Munich but police have been unable to find the suspects and are not even sure if they exist or are in the country, the Munich police chief said on Friday.
The shutting down of the stations added to jitters in many capitals as Europe ushered in the New Year with heightened security after a year of militant attacks, the biggest of which killed 130 in Paris in November.
The U.S. Justice Department said on Thursday that a 25-year-old man accused of planning to attack a restaurant in upstate New York on New Year's Eve had been arrested and charged with attempting to provide material support to Islamic State.
In New York city, police tightened security for the traditional New Year's Eve dropping of the crystal ball in Times Square, where more than a million people hailed the arrival of 2016.