"It is like a David versus Goliath struggle," one of the plaintiffs, Asmania, who like many Indonesians goes by one name, told AFP after the hearing.

The case is part of a wider international movement seeking to assign to major companies responsibility for the climate damage hurting the livelihoods of millions of people, especially in developing countries.

Oil companies have typically been the biggest targets, but climate activists are hoping the suit against Holcim will highlight the role of a lesser-known but highly polluting industry, which is responsible for around eight percent of carbon dioxide (CO2) emitted into the atmosphere each year.

Four residents of Pari island filed a suit demanding compensation from the world's largest cement firm for the damage wrought by climate change and help to fund protection measures on the island.

Asmania and another plaintiff travelled to Switzerland to take part in Wednesday's hearing at the court in Zug, where Holcim is headquartered, to determine whether or not it will consider the complaint.

It was not clear when the court would give its decision.

- 'Climate justice' -

"I feel very moved," Asmania, a 42-year-old mother-of-three, told AFP.

"I believe the judges will stand for us, so we will win."

Before the hearing, Holcim maintained that "the question of who is allowed to emit how much CO2" should be "a matter for the legislature and not a question for a civil court".

But it said Wednesday that "we await the court's decision", insisting that it was "fully committed to reaching net zero by 2050 with sustainability at the core of our strategy".

The company has not owned any cement plants in Indonesia since 2019, but the plaintiffs maintain it "shares responsibility for rising temperatures and thus rising sea levels", explained Yvan Maillard-Ardenti of the Swiss Church Aid (HEKS) NGO helping the islanders.

Environmentalists say Holcim ranks among the world's 100 biggest corporate CO2 emitters, and so bears significant responsibility for climate-related loss and damage.

The case illustrates the new face of the climate fight, as activists use the courts rather than rely on political action in the fight against global warming.

If accepted, it could be a milestone for plaintiffs from developing countries who take on industrial giants.

- 'Inspirational' -

Environmentalists have said 11 percent of the 42-hectare (104-acre) island of Pari has already disappeared in recent years, and it could be completely under water by 2050 due to rising sea levels.

The islanders say saltwater floods have surged in scale and frequency, battering homes and damaging livelihoods.

Asmania has already lost her seaweed farm because of flooding, which has also blighted her fish farm.

"We are the climate victims, but we are not contributing to big emissions," she said.

"It is our survival that is at stake."

The four plaintiffs are seeking 3,600 Swiss francs ($4,500) each from Holcim for damages and for protection measures such as planting mangroves and constructing breakwater barriers.

HEKS stressed that the amount was only equivalent to 0.42 percent of the actual costs -- in line with estimates that Holcim is responsible for 0.42 percent of global industrial CO2 emissions since 1750.

In addition, the plaintiffs are demanding a 43 percent reduction in Holcim's greenhouse gas emissions by 2030 and a 69 percent reduction by 2040.

"The contrast is enormous between this island, which is disappearing, and the wealth we have here in Zug," Maillard-Ardenti said.

"This wealth comes from large multinationals like Holcim, (which) have never paid a single franc in climate compensation," he said, stressing that the total 14,000 francs requested by the plaintiffs was "less than an hour's salary for the chairman of Holcim's board".