An unknown number of people have been killed and injured in a stabbing attack at a festival in the city of Solingen in western Germany, the news agency dpa reports.

The attack happened about 9.45pm on Friday, local time. It is not immediately clear how many casualties there are.

The local Solinger Tagblatt newspaper reported authorities called on people to leave downtown Solingen and that one of the festival organisers, Philipp Müller, said on a stage that emergency workers were fighting for the lives of nine people.

The dpa report cited unidentified police sources as saying the weapon was believed to be a knife and no one had yet been arrested.

The festival marking the city’s 650th anniversary began on Friday and was supposed to run through Sunday.

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

—AAP