Swiss voters have narrowly backed proposals to reintroduce immigration quotas with the European Union, a Swiss television has reported.

The result on Sunday, which was backed by 50.5 percent voters, calls into question bilateral accords with the EU and could irk multinational companies, Reuters news agency reported.

In a nail-biting vote, 50.5 percent backed the so-called "Stop mass immigration" initiative, which also won the required majority approval in more than half of Swiss cantons or regions, Swiss television said.

The vote, which comes 12 years after a free movement of people agreement with the EU came into force, could hurt the Swiss economy dependent on foreign professionals by increasing red tape and jeopardising bilateral accords with the bloc, according to Reuters news agency. 

The measure means the Swiss government must renegotiate within three years a deal with Brussels that since 2007 has given most EU citizens free access to the country's labour market.

It could also put Switzerland, which prides itself on a long humanitarian tradition, at odds with international accords on asylum.

To maintain its neutrality, Switzerland is not a member of the European Union, but has long-standing agreements with the EU, including its immigration policy based on free movement of people to and from the EU, as well as allowing in a restricted number of non-EU citizens.

Source: Agencies