A threatened attack against a mall in the western city of Essen is linked to the Islamic State extremist group, Germany's interior minister said Sunday.

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 ISIS 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.

De Maiziere also confirmed a connection between "somebody who had traveled there from Germany and indications and assignments from that region."

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.

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.

Germany has been on the edge following a series of attacks in public places over the past year. When a man went on a rampage with an axe on Friday night at Duesseldorf's main station and injured 10 people, hundreds of police officers were deployed to the scene, even though it later turned out that he had no links to extremists, but was suffering from psychological problems.