All male visitors to a Kylie Minogue concert were frisked before entering the venue in Cologne on Tuesday, as police armed with submachine guns monitored proceedings. Authorities reinforced security due to a possible attacker from Belgium, according to the police.

"The organizers contacted us due to a possible threat scenario based on evaluating social media platforms," a police spokesman told the German news agency DPA. "When it comes to things like that, we cannot simply stand by," he added.

At the same time, authorities emphasized that the concert passed off "without any disturbance."

The mentally disturbed man reportedly made threats against the 50-year-old singer, according to Germany's mass circulation Bild newspaper. Pictures of the suspect were posted at the venue. German police also contacted colleagues in Belgium.

Minogue is currently performing in Germany as part of a wider tour across Australia and Europe. The Tuesday concert, held before some 2,500 people in Cologne, followed a performance in Berlin. The singer is set to perform in Hamburg on Saturday before continuing on to Copenhagen and Amsterdam.