A Swiss court has upheld the conviction of two former top officials in the country's strongest political party for racial discrimination over a campaign poster that proclaimed "Kosovars cut up the Swiss!"

The nationalist Swiss People's Party has long courted controversy with posters on immigration issues. The ad in question, displayed during a 2011 campaign to curb immigration, referred to an incident in which a man from Kosovo had wounded a Swiss man with a knife. It also included an image of several people walking over a Swiss flag.

A Bern court convicted the party's then-general secretary, Martin Baltisser, and his deputy Silvia Baer of racial discrimination and fined them. The Federal Tribunal dismissed their appeals Thursday.

In a 2014 referendum, voters narrowly approved immigration curbs sought by the party.