Swiss voters narrowly accepted an overhaul of the country's passport system to include travel documents equipped with biometric data. The tight result reflects widespread concern of government intrusion into people's privacy.
According to official results Sunday, the biometric passport was approved by 50.1 percent of voters, against 49.9 percent.
Europe's control-free travel zone requires countries to register citizens' facial and fingerprint images on an electronic chip in the passport.
Non-EU Switzerland joined the so-called Schengen agreement last year.
The political left and nationalists fear biometric passports are not secure and personal data could be abused.
The Swiss need biometric passports to stay on the US visa waiver program.