Three people were killed and four severely wounded in a knife attack at a festival in the western German city of Solingen on Friday, according to a spokeswoman for the police in nearby Duesseldorf.

Police have launched a "major operation" to find the suspect, who is on the run, the spokeswoman said, adding that a "wide area" had been cordoned off.

There was a large police presence at the scene including special forces and a helicopter, according to an AFP photographer.

The attacker had "stabbed people indiscriminately with a knife", the Bild daily reported.

The festival was part of a series of events to celebrate the city's 650th birthday.

In a statement posted online, Tim-Oliver Kurzbach, the mayor of Solingen, said the whole city was in "shock, horror and great grief".

"We all wanted to celebrate our town's anniversary together and now we have to mourn the dead and injured," he said.

'Brutal and senseless'

Kurzbach thanked the emergency services for their work at the scene and expressed sympathy with those who had witnessed the attack.

"It tears my heart apart that there was an attack on our city. I have tears in my eyes when I think of those we have lost. I pray for all those who are still fighting for their lives," he said.

Hendrik Wuest, the premier of North Rhine-Westphalia state, also expressed his "shock and grief" in a post on social media platform X. 

"An act of the most brutal and senseless violence has struck at the heart of our state," he said. 

"The whole of North Rhine-Westphalia stands by the people of Solingen, especially the victims and their families."

Solingen is a city of some 150,000 people located an equal distance from Duesseldorf and Cologne.

People had gathered in the town on Friday evening for the first day of a three-day "Festival of Diversity", according to the event's website.

The festival was set to feature music, street theatre, variety shows and comedians in the city center and several other areas, it said. 

Up to 75,000 visitors were expected to attend over the three days.

Festival cancelled

The Solinger Tageblatt newspaper reported that one of the co-organizers of the festival had come on stage to call off the event. 

The crowd were also asked to leave the city center, it said.

Following the announcement, thousands of attendees cleared the area, the paper reported, with a journalist at the scene describing the atmosphere as "ghostly".

"People left the scene in shock, but calmly," Philipp Mueller, one of the organizers, told the newspaper. 

A witness who spoke to the Tageblatt said he was a few meters from the attack, not far from the stage, and "understood from the expression on the singer's face that something was wrong".

"And then, a meter away from me, a person fell," said the man, Lars Breitzke, who at first thought it was someone who was drunk. 

But when he turned around, he saw other people lying on the ground and several pools of blood, he added.

Festival organizer Mueller later told the Tageblatt that the rest of the festival would also be cancelled.

"We've just informed all the artists and stand operators," he said.

Germany has seen a series of knife attacks over the past 12 months, with Interior Minister Nancy Faeser promising to crack down on knife crime.

A police officer was killed and five people were wounded in a knife attack at a far-right rally in the city of Mannheim in late May.

by Ina Fassbender with Femke Colborne, AFP