Voting is under way on the French Pacific islands of New Caledonia on whether to become an independent nation, in a closely watched test of support for France in one of its many territories scattered around the globe.

New Caledonia, which is 18,000 kilometres (11,000 miles) from France, is home to a quarter of the world’s known supplies of nickel – a vital electronics component – and is a strategic foothold for France in the Pacific.

Home to 269,000 people, New Caledonia is one of a handful of French island outposts – a legacy of the country’s 19th-century empire – which retain strategic importance.

Voting in New Caledonia’s 284 polling stations opened at 8am local time on Sunday and was to end at 6pm, with results expected Sunday evening.

But there are fears the referendum, which 175,000 people are eligible to vote in, could inflame tensions between indigenous Kanak people, who tend to favour independence, and the white population, which boiled over into deadly violence in the 1980s.

The quasi-civil war claimed more than 70 lives. It led to the 1998 Noumea Accord which paved the way for the steady devolution of powers as well as Sunday’s referendum.

On Friday, separatist activists drove along Noumea’s waterfront in a convoy of around 20 cars, waving the Kanak flag to cries of “Kanaky” – their name for New Caledonia.

Separatists have urged Kanak voters to choose self-determination, throwing off the shackles of “colonial” authorities in Paris. But indigenous people make up less than 50% of the electorate and some Kanaks back staying part of France, not least due to the 1.3 billion euros ($1.5 billion) the French state gives to the islands every year.

“I’m not sure we have all the assets we’d need to succeed,” said Marc Gnipate, a 62-year-old pensioner.

Polls suggest 63 to 75% of voters will opt against breaking away from France, which claimed the islands in 1853 and once used them as a penal colony.

Under the 1998 deal, in the event of a “no” vote two further referendums on independence can still be held before 2022.

French President Emmanuel Macron is set to give a televised address after the results on Sunday.

He has largely stayed clear of the campaign, but declared during a visit to Noumea in May that “France would be less beautiful without New Caledonia”.

Macron also raised concerns over increasing Chinese influence in the Pacific, where Beijing has invested heavily in Vanuatu, a territory which broke from France and Britain in 1980.

Accusing the US of “turning its back on the region in recent months”, Macron said China was “building its hegemony step by step” in the Pacific – suggesting an independent New Caledonia could provide Beijing’s next foothold.

Australia has also expressed concerns about China’s activities in neighbouring island states – which the Lowy Institute thinktank estimates received $1.78bn in aid from Beijing from 2006-16 – boosting its own spending in response.