Three people have been killed and at least five were seriously wounded in an attack at a festival in the western German city of Solingen, police said.

Witnesses alerted police shortly after 9.30pm on Friday to an unknown perpetrator having wounded several people with a knife on a central square, the Fronhof.

Police said that the perpetrator was on the run, German news agency dpa reported.

It cited unidentified police sources as saying the weapon was believed to be a knife.

The attack happened on a central square, the Fronhof.

One of the festival organisers, Philipp Muller, appeared on stage and asked festival-goers to “go calmly; please keep your eyes open, because unfortunately the perpetrator hasn’t been caught”.

He said many people had been wounded by “a knifeman”.

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.

The Festival of Diversity, marking the city’s 650th anniversary, began on Friday and was supposed to run through to Sunday, with several stages in central streets offering attractions such as live music, cabaret and acrobatics.

Solingen has about 160,000 residents and is located near the bigger cities of Cologne and Duesseldorf.