An old steam roller painted with the EU stars stands in Kloten, Switzerland. The choice by Swiss voters to reimpose curbs on immigration is sending shock waves throughout the European Union, with EU leaders warning the Swiss had violated the sacred principle of Europeans freedom of movement. (AP Photo/Keystone,Steffen Schmidt)

Brussels - The European Union will have to review its relations with Switzerland as a result of a Swiss referendum decision to curb immigration, top politicians warned Monday.

A slim majority of voters in non-EU country Switzerland voted Sunday in favour of introducing quotas for foreigners, which runs counter to existing Swiss-EU agreements on free movement. “The free movement of people is a sacred freedom for the EU,” said Pia Ahrenkilde, a spokeswoman for the bloc's executive, the European Commission.

“We cannot accept such restrictions without implications for the rest of the agreements we have with Switzerland.”

The bloc is waiting to spell out those consequences until after Swiss authorities officially announce how they will react to the referendum, which requires the government to act within three years.

“We should assess the consequences without foaming at the mouth,” German Foreign Minister Frank-Walter Steinmeier told journalists in Brussels, where he discussed the issue with his 27 EU counterparts.

One thing that is not up for consideration is renegotiating free movement provisions to accommodate the Swiss referendum outcome, said an EU source, who was speaking on condition of anonymity.

“The introduction of quotas in our agreement (with Switzerland) is completely excluded,” he said.

He indicated that Swiss access to EU research and education programmes is threatened, since this is linked to Bern lifting migration restrictions on citizens from the EU's newest member, Croatia - a move now expected to be put on hold.

Switzerland, which is surrounded by EU states, has deals with the bloc governing wide-ranging ties in everything from trade to rail transport.

The two sides were also poised to start negotiating a new overarching agreement; it remains to be seen how it will be affected.

“As it is not possible to cherry-pick, Switzerland is of course putting its entire set of agreements with the EU in danger,” Austrian Foreign Minister Sebastian Kurz said in Brussels.

“Switzerland did not do itself a favour,” Steinmeier added. “Economic growth is essentially based on open doors and immigration from the EU.”

But 50.3 per cent of voters in Switzerland backed immigration quotas on Sunday, reflecting a strong public opinion that the inflow of foreigners overburdens the job and housing markets, as well as schools, hospitals, trains and roads.

The EU estimates that there are about 1 million EU citizens living and working in Switzerland, while about 430,000 Swiss citizens are doing so in the 28-country bloc. Italian, German and Portuguese are the largest groups among immigrants in Switzerland, where nearly a quarter have foreign passports.

The EU source declined to speculate what could happen if the Swiss government in the end chose to implement the quotas and violate its agreements with the bloc, saying simply that “it would make life much more complicated” for everyone. The Swiss government and business groups had campaigned against the immigration-restriction plan of the far-right Swiss People Party, arguing that the country could not afford to risk its economic ties with the EU.

The head of the Swiss Employers Federation, Valentin Vogt, warned that highly qualified job seekers with offers in several countries would shun Switzerland. Up to 80 000 immigrants have entered the wealthy country annually in the last decade. Two-thirds of immigrants come from the EU.

Migration has become a bone of contention in the bloc ahead of European elections in May, which are expected to deliver gains foreurosceptic and far-right political parties. The leader of Britain's anti-immigration, anti-EU UK Independence Party was among those who welcomed the result of the Swiss poll.

“This is wonderful news for national sovereignty and freedom lovers throughout Europe,” said Nigel Farage, who is also a EU parliamentarian.

“A wise and strong Switzerland has stood up to the bullying and threats of the unelected bureaucrats of Brussels.” Switzerland is also a member of the free-travel Schengen zone.

It was not immediately clear on Monday if and how this could be affected by the referendum vote.