Six journalists face trial in France for invasion of privacy over topless photos of the Duchess of Cambridge published in 2012, according to French media reports.

The snaps were taken of Prince William and Kate Middleton with a long lens on a balcony of a private residence while they were on holiday in the southern Luberon region.

The Duke and Duchess pressed at the time for criminal charges in France to try to prevent wider publication of the pictures.

The reports said those covered by the case would include senior staff at French regional newspaper La Provence, Closer Magazine, and Closer's parent company - Silvio Berlusconi's Arnoldo Mondadori Editore publishing group.

Neither La Provence nor Mondadori could immediately be reached by Reuters for comment.

The French trial for the photos will be held in 2017.