The European Union called on Switzerland Monday to respect its international obligations after voters endorsed a far-right bid to automatically expel foreign residents convicted of certain crimes.

"We take note of yesterday's results, we are going to study how these results will be implemented in Switzerland," said a spokeswoman for foreign affairs chief Catherine Ashton.

Ashton was confident that Switzerland "would continue to respect its obligations of international treaties," the spokeswoman said.

On Sunday, 52.9 percent voted in favour of automatic expulsions and 47.1 percent were against, with the country's German-speaking majority largely backing the proposal. Only six of the 26 cantons rejected the initiative.

Exactly a year ago, Switzerland shocked the world by agreeing to ban the construction of new minarets, which was another proposal backed by the far-right Swiss People's Party (SVP).

The result came as European Commission president Jose Manuel Barroso warned Sunday of rising nationalism in Europe, sometimes fanned by weak governments.

"It worries me that today in Europe there is an upsurge of populism, of extremes," he said in a radio interview.

Swiss Justice Minister Simonetta Sommaruga had said the government would set up a working group to examine how the new rule could be implemented in a way that complies with the Swiss constitution and international conventions.

Judges can already issue expulsion orders for foreign criminals but the SVP's initiative goes further by requiring automatic expulsions for those found guilty of "rape, serious sexual offence, acts of violence such as robbery," drug trafficking and "abuse of social aid."

According to the Federal Office of Migration, about 350 to 400 people are expelled every year but this figure would rise to 1,500 with the adoption of the new initiative.

Frederic Esposito, a political expert at Geneva University's European Institute, said the Swiss government had limited room for manoeuver given international treaties its constitution.

"It all depends on whether the SVP will accept more flexibility," he said.

The case showed the limits of the Swiss direct democracy system and a weakness in the government, Esposito said.

Newspapers across Europe criticised the Swiss decision, with Belgian newspaper Le Soir saying that "Switzerland has once against chosen the radical `1road."

With the vote, "the Swiss have once again slapped the EU in the face," as the expulsion is "absolutely incompatible with the bilateral accord of free movement of people which links Switzerland to EU," said the newspaper.

The vote could "put all bilateral accords in question," it added.

Swiss broadsheet Le Matin said the far-right campaign was successful as the party had become a "real war machine, with a perfect propaganda service, incomparable financial means, dedicated politicians and simplistic but terribly efficient messages."