A Turkish man must give up his Swiss passport obtained after marrying a Swiss national because he has a second family in Turkey, a court has ruled.
The Swiss Federal Court said the man was found to have a partner in Turkey with whom he had two daughters when he was granted Swiss citizenship in 2003.
Naturalisation by marriage required monogamy by both parties, it ruled.
It is unclear whether the man's Swiss wife, to whom he had been married for 26 years, knew of his second family.
The court said that the man - who has not been identified - "was virtually living a bigamous life, which is not allowed in Switzerland", the AFP news agency reports.
It upheld an earlier decision by Switzerland's Federal Office for Migration to strip the man of his Swiss citizenship.