Thomas de Maiziere told public broadcaster ARD that Germany's domestic intelligence service, the Federal Office for the Protection of the Constitution, had received "tips of an attack and passed them on" to local security authorities in Essen.
"The case was evaluated several times ... And it couldn't be eliminated that there could have been a concrete attack at this mall. This was prevented," de Maiziere said.
Daily papers Bild, Westdeutsche Allgemeine Zeitung and public broadcaster WDR had reported earlier, citing anonymous security sources, that a German fighter with the IS in Syria had contacted via online messenger a group of fighters based in Germany and abroad and tried to motivate them to attack the mall Saturday.
The mall in Essen, one of the biggest in Germany, didn't open Saturday. About 100 heavily armed police officers positioned themselves around the compound to prevent anyone from entering.
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The apartments of two men were later searched in nearby Oberhausen and they were detained and interrogated. One was released Saturday, police said, with no details.
The mall in downtown Essen will open again on Monday because there is no longer an increased threat of an attack, the German news agency dpa reported.