German police closed streets in Cologne's city center on Monday morning following an explosion in front of a popular nightclub.
The explosion occurred at approximately 5:50 a.m. local time (0350GMT) on the ground floor of a building on the Hohenzollernring street, and damaged shop fronts and display windows.
The police said on social media that a major operation was underway, and asked people to avoid the area. No casualties were reported so far, according to local officials.
