State authorities have banned the Hell's Angels motorbike gangs in Frankfurt, on the grounds that they were engaged in criminal activity.

Boris Rhein, interior minister for the state of Hesse, accused the gangs of running drug and prosecution rackets through which they had seized control of the streets.

"This is a clear signal that we won't allow a state within the state," said Rhein, adding that the gangs were disciplined by a vow of silence.

All assets of the outlawed Westend and Frankfurt chapters of the Hell's Angels were seized under the ban. Each chapter is believed that have around 90 members.

Two other Hell's Angels groups were banned in other parts of Germany in June and last year, although gangs in the rest of Germany remain legal.