53% of Swiss voters backed a proposal to automatically deport foreigners convicted of crimes including rape or drugs trafficking.
The deportation of foreign criminals had until now been treated on a case-by-case basis.
Under the terms set by the referendum, the Swiss government would automatically be required to expel foreigners convicted of serious crimes after they have completed a prison sentence of a full year. Such criminals would also be prevented from returning to the country for up to twenty years.
Referenda are binding under Swiss law.
Foreign residents make up over 20% of Switzerland's population and include second-generation immigrants. Under Swiss law, second-generation migrants do not qualify for citizenship unless they have lived in the country for at least twelve years.
In accordance with the referendum results, a committee will now start drawing up a draft law that will be submitted to parliament for a vote. The Swiss government said it would do the necessary to ensure that the draft law "minimises" any conflict with the country's international obligations.
Right-wing initiative
The proposal, put forward by the right-wing Swiss People's Party (SVP), is seen as the latest sign of increasing hostility towards immigrants in the Alpine nation. The SVP said foreigners were responsible for nearly 60% of murders in the country last year.
The same party drummed up support last year for a ban on building of minarets in the country, drawing widespread condemnation (see 'Background'). It also notoriously displayed a picture of a group of white sheep kicking a black sheep off the Swiss flag during the 2007 federal elections.
In contrast, Swiss citizens living abroad largely voted against the deportation proposal, preferring instead a watered-down version of the law proposed by the Swiss parliament.
An international conflict?
As a member of the Schengen area, Switzerland is obliged to allow citizens of other Schengen members to live, work and study in the country. Switzerland could be accused of infringing the free movement of persons principle, a fundamental right guaranteed to EU citizens.
The new legislation could also be considered to be in breach the UN Convention Against Torture, signed by Switzerland, which requires signatories to refrain from deporting people to countries that practice torture.
As nearly half of Switzerland's 1.6 million residents come from non-European countries, there is a risk that the country could deport migrants to their countries of origin, where torture may occur.
EU reaction
A spokesperson for the European Commission said Brussels would carefully study how the results of the Swiss referendum would be translated into legislation and expressed hope that Berne would continue to respect its international obligations.
At a regular press briefing on Monday, Commission spokespeople were pressed to comment on declarations by Commission President José Manuel Barroso, who expressed concern about the rise of xenophobia in Europe.
Barroso, speaking on Monday on French radio station Europe 1, did not mention any country in particular but confirmed "a general fear precisely in this sense," a spokesperson said.
"There is today in Europe a push of populism and of extremes which is very serious and worries me. I see societies with a long tradition of openness and democracy mounting a nationalist, chauvinistic, xenophobic push, sometimes of very, very aggressive populism," said Barroso, speaking in French.
