Police in the western German city of Essen sealed off a shopping center in the center of town and ordered it to remain closed on Saturday due to concrete indications of a possible attack.
Germany is on high alert following major radical Islamist attacks in France and Belgium and after a failed asylum seeker from Tunisia drove a truck into a Berlin Christmas market in December, killing 12 people.
"Yesterday we received very serious indications from security sources that a possible attack was planned here for today and would be carried out," a spokesman for Essen police told Reuters Television. "That is why we were forced to take these measures."
Earlier, a police spokesman told a German broadcaster that they had viewed the threat as a possible "terrorist" attack.
Armed police and vans surrounded the shopping center, one of Germany's biggest with more than 200 retail outlets, but roads nearby were open to traffic.
Essen, in the industrial Ruhr region, has nearly 600,000 inhabitants.
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