The Swiss have approved a ban on the construction of minarets, according to incomplete results of voting on Sunday.
The gfs.bern polling institute said an estimated 58 per cent of voters had backed the initiative. A majority of cantons were also in support of a minaret ban.
Turnout was high at around 55 per cent.
The result, if confirmed, comes as a major surprise and a slap in the face of the government. Opinion polls ahead of the vote had predicted the ban would be rejected by 53 per cent of the electorate.
The proposal on banning minaret construction was championed by rightwing and ultra-conservative groups. The government and most political parties as well as churches and the business community came out strongly against it.
To be approved, it needed the backing of a majority of both voters and cantons.
The director of gfs.bern told Swiss French television that the issue by the end of the campaign was not minarets, but the position of Muslims in Switzerland.
Swiss Justice Minister Eveline Widmer-Schlumpf had argued strongly against a ban on minaret construction.
"The initiative is a kind of 'proxy war'. Its supporters say they are against minarets. But they want to fight what they consider creeping Islamicisation and sharia law," she said ahead of the vote.
Opponents warned that approval of the proposal would fuel Islamic extremism and damage Switzerland's image abroad, particularly in the Muslim world.
Supporters of a ban argued minarets are a symbol of an Islamic claim to power.
"The Islamic religion is intolerant, but we do not want to limit freedom of religion, we want to outlaw the political symbol," said Ulrich Schlüer, a member of the rightwing Swiss People's party and one of the leading promoters of the anti-minaret initiative.
Supporters claimed there is public concern about the growing Muslim community in Switzerland, radical imams, the role of women, as well as head scarves and other dress codes.
The number of Muslim immigrants has increased to about 350,000 (up to 4.5 per cent of the Swiss population) since the 1990s. Most of them came from the former Yugoslavia and Turkey and are considered moderates.
There are an estimated 160 mosques and prayer rooms in Switzerland, mainly in disused factories and warehouses. Only four of them have a minaret, including the mosques in Geneva and Zurich.
In the wake of heated debates at a local level about requests to build more minarets, members of the People's Party and the Federal Democratic Union collected enough signatures to force a nationwide vote.
The campaign in the run-up to the vote was marked by a provocative poster campaign, which was criticised as racist by non-governmental organisations and international bodies.
"The supporters succeeded in forcing a broader debate about integration of Muslims in Swiss society," said political scientist Claude Longchamp of gfs.bern.
A separate proposal by an alliance of peace groups and centre-left political parties to ban the export of weapons and other war materiel was rejected.
All cantons voted against the proposal, and partial results showed that it had the backing of just 32% of voters.
It is the third time in nearly 40 years that pacifists have sought to win a majority for their cause.
The pacifists, including the Group for a Switzerland without an Army, argued that arms exports are incompatible with Switzerland's foreign policy aims and traditional neutrality.
The government and most political parties had warned the initiative would cost thousands of jobs and weaken Switzerland's defence capabilities.
Aviation fuel tax
Voters appeared to have accepted a modified tax on kerosene, with 65% in favour, according to incomplete results.
The government and parliament want to use most of the revenue from a fuel tax on domestic flights for aviation safety and environmental measures.
At the moment the money – SFr40 million ($40 million) annually - is spent on road projects.
Supporters said the country's 11 regional airports would benefit from the proposed change in the constitution.
Opponents argued international flights out of Switzerland should also be subject to the proposed tax reform.