Australians stranded in New Caledonia are rationing food as they wait for a way out of the Pacific island territory, after unrest that has killed six people, a traveller from Sydney said on Saturday.

"The kids are definitely hungry because we don't really have much option of what we can feed them," Joanne Elias told Reuters by phone from a resort in the capital Noumea, where her family has been holed up since the unrest in the French-ruled territory broke out this week.

The riots have been sparked by anger among indigenous Kanak people over a constitutional amendment approved by lawmakers in Paris that would allow French people who have lived in New Caledonia for at least 10 years to vote in provincial elections, which some local leaders fear will dilute the Kanak vote.

Three nights of upheaval have resulted in burnt businesses, torched cars, looted shops and road barricades, cutting off access to medicine and food.

Three indigenous Kanak and two police officers were among those killed. A sixth person was killed and two seriously injured on Saturday during a gun battle between two groups at a roadblock in Kaala-Gomen, the French police said, without identifying the groups.

Hundreds of French police reinforcements began arriving in the territory on Friday in an effort to regain control of the capital.

Elias, who arrived in the territory on May 10 with her husband and four children, said she had been told to fill a bathtub in case water ran out, as food stocks dwindled.

"We don't know how long we're going to be here for," she said, adding that her family was among about 30 Australians stuck at the Chateau Royal resort.

The resort declined to comment on the situation, citing security reasons.

Australian Foreign Minister Penny Wong said Canberra was "working with authorities in France and New Caledonia, and like-minded partners including New Zealand, to assess options for Australians to safely depart".

In a post on social media platform X on Saturday she added that Noumea's La Tontouta International Airport remained closed and urged Australians "to exercise a high degree of caution in New Caledonia".

The New Caledonia government said on Friday the island had stocks of food for two months and the problem was distribution.

Operations to supply food and medicine to the public will begin with teams including specialists in mine clearing removing road barricades that were booby-trapped by activists, French officials have said.