An attacker with a knife has killed three people and seriously wounded at least five at a festival in the western German city of Solingen.
Witnesses alerted police shortly after 9.30pm on Friday local time (5.30am Saturday AEST) to an unknown attacker having wounded several people indiscriminately with a knife on a central square, the Fronhof.
Police said the perpetrator was on the run, and they had only very little information on the man so far.
They believe the stabbings were carried out by a lone attacker.
One of the festival organisers, Philipp Müller, appeared on stage and asked festivalgoers to "go calmly. Please keep your eyes open, because unfortunately the perpetrator hasn't been caught".
Police said the perpetrator of the attack is still on the run. Source: AAP / Gianni Gattus/AP
At least one helicopter was seen in the air, while many police and emergency vehicles with flashing blue lights were on the road and several streets were closed off.
Police put the number of seriously injured at five.
The region's top security official, Herbert Reul, gave a figure of six as he visited the scene in the early hours of Saturday.
"None of us knows why" the attack took place, said Reul, who is the interior minister of North Rhine-Westphalia state.
"I can't say anything about the motive now" and it isn't clear who the assailant was, he said, but the attacker left the scene "relatively quickly".
Herbert Reul, the region's top security official, told media "none of us know why" the attack took place. Source: AAP / Thomas Banneyer/AP
"It breaks my heart that an attack on our city happened," he wrote.
Local newspaper Solinger Tageblatt quoted Celine Derikartz, its reporter covering the festival, as saying that "the atmosphere is spooky".
She said a party atmosphere had turned to shock within minutes and she saw festivalgoers weeping.
The festival, marking the city's 650th anniversary, started on Friday and was supposed to run through Sunday, with several stages in central streets offering attractions such as live music, cabaret and acrobatics.
The city cancelled the rest of the festival after the attack.
Solingen has about 160,000 residents and is located near the bigger cities of Cologne and Duesseldorf.
