Germany is increasing security at airports and railway stations in light of “concrete indications” of terrorist attacks being planned for the end of November.
Interior Minister Thomas de Maiziere said it followed a tip-off from another, unnamed country.
Germany had information on “sustained efforts” by Islamist extremists to carry out attacks, he said.
He said the extra security would remain in place “until further notice”.
“There are grounds for concern, but not for hysteria,” Mr de Maiziere told a news conference in Berlin.
The BBC’s Stephen Evans, in Berlin, says Germany downplayed the risk when the US increased its terrorism alert warning level for Europe three weeks ago.
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