German police said on Saturday they are still searching for an unknown assailant hours after he killed three people and wounded others in a stabbing attack at a festival in the western city of Solingen.

Witnesses alerted police shortly after 9:40 p.m. local time to an unknown perpetrator attacking several people indiscriminately with a knife on a central square, the Fronhof. Eight people were also injured, five of them seriously, the police said in an update early on Saturday.

Police said the attacker was on the run, and so far had only very little information on the man they believe was acting alone. 

"Both victims and witnesses are currently being questioned. The police are currently searching for the perpetrator with a large team," police said.

One of the festival organizers, Philipp Müller, appeared on stage to say many people had been wounded by "a knifeman" and asked festival goers to "go calmly; please keep your eyes open, because unfortunately the perpetrator hasn't been caught."

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.

"None of us knows why" the attack took place, said Herbert Reul, the region's top security official 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 also said, adding the attacker had left the scene "relatively quickly."

'It breaks my heart,' says mayor

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 heart that an attack on our city happened," he added.

The 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 festival goers weeping.

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.

The city has 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.

Fatal stabbings and shootings are relatively uncommon in Germany. 

German Chancellor Olaf Scholz said on Saturday that the perpetrator of the attack must be caught quickly and punished with the full force of the law.

"The attack in Solingen is a terrible event that has shocked me greatly," he said on X.

"I have just spoken to Solingen's mayor, Tim Kurzbach. We mourn the victims and stand by their families."

German President Frank-Walter Steinmeier also spoke to the mayor of Solingen on Saturday morning.

"The heinous act in Solingen shocks me and our country. We mourn those killed and worry about those injured and I wish them strength and a speedy recovery from all my heart," Steinmeier said in a statement.

"The perpetrator needs to be brought to justice. Let's stand together — against hatred and violence."

Germany's top security official, Interior Minister Nancy Faeser, recently proposed toughening weapons laws to allow only knives with a blade measuring up to six centimetres to be carried in public, rather than the length of 12 centimetres, which is allowed now.

"We are deeply shocked by the brutal attack on the city festival in Solingen," Faeser said in a statement Saturday morning.

"Our security authorities are doing everything they can to catch the perpetrator and establish the background to the attack."