Geneva — Switzerland was voting Sunday in national elections that could see unprecedented gains for parties demanding bold climate action and a possible slip for the anti-immigrant right-wing.

In a country that recently held a funeral march for an iconic glacier that has nearly vanished due to melting, opinion polls point to "green wave" vote.

Climate change displacing immigration as the top concern among voters is one of the most significant shifts in recent Swiss political history, according to the Sotomo political research institute.

The Swiss People's Party (SVP), which has repeatedly been accused of demonising migrants, is still likely to remain the largest parliamentary party, with opinion polls giving it over 27 percent support in the wealthy Alpine nation.

But that is down from the 29 percent the SVP garnered in 2015.

The Green Party, which won just over seven percent in 2015, is now backed by nearly 11 percent of voters, according to a poll released this month by public broadcaster RTS.

Meanwhile, the Green Liberals — an environmentalist party with libertarian socio-economic policies — has also seen its fortunes rise, with the RTS poll giving it over seven percent support, compared to less than five percent four years ago.

Even if the Greens do not manage to secure a cabinet seat, the parties currently in government have pledged to do more to combat climate change, except for the SVP which has denounced "climate hysteria" in Swiss politics.

Swiss were voting across the country's 26 cantons on Sunday although the vast majority of people cast ballots by mail.

If the environmentalist parties match or outperform their poll numbers, they could, through an alliance, force their way into the executive branch for the first time.

Under Switzerland's unique political system, the election will decide the 200 lower house lawmakers and 46 senators elected to four-year terms, but the make-up of the executive Federal Council will not be decided until Dec. 11.

The country's so-called "magic formula" sees the council's seven cabinet positions divided among the four leading parties.

Currently, six cabinet seats are shared equally between the SVP, the Socialist Party and the right-leaning Free Democratic Party, with the centrist Christian Democrats holding the seventh seat.

The presidency rotates each year.

Analysts have questioned whether an environmental alliance could join the cabinet, in part because there is no guarantee that the leftwing Greens and the libertarian Green Liberals could agree on a unity candidate.

But Green Party vice president Lisa Mazzone told AFP that, given the severity of the climate emergency, her bloc intends to be "a force" in the executive.

On top of the funeral held for the Pizol glacier last month, a recent study by the Swiss Academy of Science showed that the nation's glaciers have lost a tenth of their volume in the past five years alone.

In a separate study, Zurich's ETH university indicated that more than 90 percent of the roughly 4,000 glaciers dotted throughout the Alps could disappear by the end of this century if greenhouse gas emissions are not reined in.

Turnout in Swiss national elections has not passed 50 percent since 1975, prompting jokes among some political observers that abstainers have been the country's largest bloc for more than four decades.

Mazzone said the Green strategy has relied on mobilizing "a dormant electorate" by targeting young people who have stayed away from politics but are increasingly worried about climate change. — AFP