After emissions scandals at Volkswagen and other German carmakers, several German cities have imposed bans on older diesel vehicles. The first ban took effect in Hamburg in May.

In September, a lower court had ordered Frankfurt, Germany's financial centre, to ban highly-polluting, older diesel vehicles from the city centre from February.

The case was one of several brought by environmental group Deutsche Umwelthilfe (DUH).

But the Hesse Administrative Court in Kassel said on Tuesday it had decided to allow the state of Hesse to appeal the lower court's decision, citing "serious doubt over its validity."

A spokesman for the Kassel court said a new hearing was not expected before February.

(Reporting by Christoph Steitz and Sabine Wollrab. Editing by Jane Merriman)