SOLINGEN, Germany — Three people were killed and four were seriously wounded in an attack on Friday at a festival in the western German city of Solingen, police said.

Police said that the perpetrator was on the run, German news agency dpa reported. It cited unidentified police sources as saying the weapon was believed to be a knife. The attack happened on a central square, the Fronhof.

Mayor Tim Kurzbach said in a Facebook post that “this evening, we in Solingen are all in shock. We all wanted to celebrate our city’s anniversary together and now have dead and wounded to lament.”

“It breaks my heard that an attack on our city happened,” he added.

The “Festival of Diversity,” marking the city’s 650th anniversary, began on Friday and was supposed to run through Sunday, with several stages in central streets offering attractions such as live music, cabaret and acrobatics.

Solingen has about 160,000 residents and is located near the bigger cities of Cologne and Duesseldorf.