A knife attack at a German event resulted in three fatalities and five critical injuries, according to authorities.

They said they thought the stabbings were committed by a lone attacker and added that the "perpetrator" had left the scene and was still at large.

In the western city of Solingen, at around 9.45 p.m. local time on Friday, passersby were allegedly randomly stabbed in a market area where live bands were performing.

Police put the number of seriously injured at five, but the region's top security official, Herbert Reul, gave a figure of six as he visited the scene in the early hours of Saturday.

Mr Reul told reporters it was a targeted attack on human life but declined to speculate on the motive.

"None of us knows why" the attack took place, said Mr Reul.

"I can't say anything about the motive now" and it isn't clear who the assailant was, he also said, adding that the attacker had left the scene "relatively quickly".

According to  news' European correspondent Siobhan Robbins, a police operation in the area is still ongoing.

To commemorate the 650th anniversary of the 160,000-person city, people had congregated for the Festival of Diversity, which got underway on Friday.

It was scheduled to continue until Sunday, with live music, cabaret, and acrobatics being featured on a number of the city's stages.