Three people were killed and four injured after a knife attack during the 650 celebrations - the anniversary of the German city, reported DPA, quoted by BTA.
A man arbitrarily attacked passers-by with a knife at the city festival, the "Bild" newspaper reported.
According to witness statements, the perpetrator, who looked like an Arab, fled the crime scene.
The police have launched a large-scale search for him. The city holiday was canceled and a police helicopter was hovering over the cordoned off area.
As reported by "Sollingen tageblatt" one of the organizers of the festival said that the rescue service was fighting for the lives of nine people.
Solingen Mayor Tim Kurzbach expressed his shock after the deadly attack.
"Tonight, all of us in Solingen are in shock, fear and great sadness,”, he wrote on the city's Facebook page.
"We all wanted to celebrate the anniversary of our city together, and now we have to mourn the dead and wounded,”, he said.
"I pray for all those who are still fighting for their lives,”, he wrote.
Kurzbach also offered his condolences to those who witnessed the attack before thanking the emergency services and police for their service.
"I beseech you, if you believe, pray with me, and if you do not believe, then hope with me.
Police sources said the attack took place at the Frohnhof, a market in the city center where a live music stage was located.
Thousands of people left the area after authorities urged residents to remain calm and return to their homes, local newspaper "Solinger Tageblatt” reported.
North Rhine-Westphalia state premier Hendrik Wust said the province was united in shock and grief after the attack in Solingen, which left three people dead and four injured.
"In these dark hours, the hearts and minds of the people of our province and beyond are in Solingen, where an act of brutal and senseless violence has struck the heart of our province,” he said in a post in "Ex".
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He said that all of North Rhine-Westphalia supports the residents of Solingen, especially the victims and their families.
„I am very grateful to the numerous rescuers and our police, who are fighting for human life in these minutes,” said Wust.