Basel city authorities have banned as racist a poster which the rightwing People's Party planned to use in its anti-minaret campaign.
The poster shows a woman in a burka and a Swiss flag pierced by minarets springing up out of the ground.
An initiative to forbid the construction of minarets in Switzerland comes to a nationwide vote on November 29.
A spokesman for the construction and traffic department of the half-canton of Basel City said the decision to ban it in publicly-owned spaces was based on a law against spreading racist ideologies or classing groups by ethnic, religious, cultural or physical characteristics.
The committee behind the anti-minaret initiative reacted angrily, describing the decision as "purely arbitrary, coming from the left" and said it was an attack on free speech.
The chairman of the committee said they would fight the decision. He said the posters would go up on private ground and flyers would be distributed.
Meanwhile other cities are still undecided about what attitude to adopt towards this and other anti-minaret posters.
Lucerne, Zurich and Winterthur are waiting for an expert opinion of the Federal Commission against Racism before taking a decision.
swissinfo.ch and agencies