Germany's match against the Netherlands has been called off after information a bomb attack was planned, according to police in Hanover.
The city's police chief Volker Kluwe told German television that authorities have "concrete evidence that someone wanted to set off an explosive device in the stadium."
"The key warning reached us about 15 minutes before the gates opened," he told public broadcaster NDR.
He urged people to keep away from stadiums and not move in large groups.
Meanwhile, the city's main train station was partially closed following reports that a suspicious object was found in a train.
Germany's Bild newspaper quoted a police spokeswoman as saying the object was either "a very convincing dummy or a genuine explosive."
The object has now been destroyed in a controlled explosion, according to German media reports.
A second stadium in Hanover, where the popular German band Shne Mannheims was due to play, was also evacuated amid heightened security fears.