Three people have been killed and another four seriously injured in a knife attack in the western German city of Solingen, police say.

The attack happened during a festival in the city centre on Friday evening. The attacker is reported to be still at large.

Bild website says a man randomly stabbed passers-by. A huge manhunt is now under way, with police helicopters seen hovering above the city.

The industrial city was celebrating 650 years since it was founded.

The city authorities asked people to leave the Fronhof market area, as police set up security cordons, following the attack at about 22:00 local time (21:00 BST).

Emergency crews at the scene were seen treating the injured, media reports said.

Police later deployed 40 tactical vehicles in the hunt for the stabbing suspect, according to Bild.

The vehicles are being commanded by SEK (Special Task Force) officers.

Roads have been blocked, and residents asked to stay indoors as officers carry out their search.

Philipp Müller, one of the festival organisers, said the emergency crews were fighting for the lives of nine people, the Solinger Tageblatt newspaper reports.

"People are shocked, but left the square peacefully," Mr Müller said.

Eyewitness Lars Breitzke told the newspaper that he knew something was wrong when he saw a singer on stage with a strange expression on their face.

"And then a person fell over just a metre away from me," he said.

The attacker is believed to have deliberately stabbed his victims in the neck, German media report.

Police spokesman Alexander Kresta was quoted by Spiegel website as saying "we are currently assuming that it was one person" after talking to numerous eyewitnesses.

In a Facebook statement, Solingen Mayor Tim Kurzbach said: "Tonight all of us in Solingen are in shock, horror and great sadness. We all wanted to celebrate our city anniversary together and now we have to mourn the dead and injured.

"It breaks my heart that an attack has happened in our city. I have tears in my eyes when I think of those we've lost. I pray for all those still fighting for their lives. Also my greatest sympathy for all those who had to experience this, these images must have been horrific."

Speaking to the BBC later on Friday, Solinger Tageblatt's deputy editor Björn Boch said the celebrations had been "supposed to last for three days, and the city expected 25,000 people every night.

"The city was just packed with people," he said, estimating that "a few thousand people" were at Friday's free event.

The celebrations have now been cancelled.

Solingen - a city in North Rhineland-Westphalia famous for its steel industry - has about 160,000 inhabitants. It lies about 15 miles (25 km) east of Düsseldorf and north-east of Cologne. (BBC, excluding headline)

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