French police reinforcements have started arriving in New Caledonia as part of a massive operation to regain control of the capital Noumea.
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The number of police and gendarmes on the French-ruled island will rise to 2700 from 1700 by Friday evening.
After rioting that began on Monday resulting in four deaths and hundreds of arrests, Thursday night was relatively calm, France's High Commissioner Louis Le Franc told reporters on Friday.
There were still points of confrontation and concern in the city of Noumea, he said.
Operations to supply food and medicine to the public will begin with teams, including specialists in mine clearing, removing road barricades that have been booby trapped by activists.
Rioters angry with an electoral reform have burnt businesses, torched cars, looted shops and set up road barricades over three days, cutting off access to medicine and food, authorities said.
"Our calls for calm, peace and reconciliation are beginning to be heard ... It is important that those who are at the origin of the clashes, of the blockages, hear this," Le Franc said.
France has declared a state of emergency on the island, put at least 10 people under house arrest and banned TikTok."The situation in New Caledonia remains very tense, with looting, riots, fires, attacks which are unbearable," French Prime Minister Gabriel Attal told reporters.
France will "show the utmost firmness towards looters and rioters" and toughen sanctions, he said.
Rioting erupted over a new bill, adopted by MPs in Paris on Tuesday, that will let French residents who have lived in New Caledonia for 10 years vote in provincial elections.
Some local leaders fear the move will dilute the indigenous Kanak vote.
Electoral reform is the latest flashpoint in a decades-long tussle over France's role in the mineral-producing southwest Pacific island 1500km east of Australia.
The government in Paris repeated past mistakes by not heeding warnings over the reform, said Dominique Fochi, secretary general of the Caledonian Union, a branch of the pro-independence FLNKS party which has called for calm but wants the reform shelved.
"We spoke in the void, and now things have exploded," Fochi told Reuters.
France annexed New Caledonia in 1853 and gave the colony the status of overseas territory in 1946.
New Caledonia is the world's No. 3 nickel miner but its nickel industry is in crisis.
Economic disparities also fuelled the riots, Fochi said.
Attal said the French government would step in to help mitigate the economic effects of the crisis.
The local chamber of commerce has estimated the cost of damage caused by the riots at 200 million euros ($A326 million), broadcaster NC La 1ere said.
"Caledonia will have a hard time recovering from this crisis ... Everything, 80 per cent, is destroyed," said Noumea resident Yoan Fleurot, who has witnessed looting.
Armed forces were protecting New Caledonia's two airports and port, France's High Commissioner Louis Le Franc said, adding roads in Noumea were blocked by barricades of burning cars and car carcasses, some rigged with booby traps.
There were also confrontations overnight between members of Field Action Co-ordination Cell (CCAT), which organised the protests, and self-defence groups, he said.
Three young Kanaks have been killed in the riots, and a 22-year-old police official died after being shot in the head as he was talking to protesters, French Interior Minister Gerald Darmanin said.
Another gendarme was killed in an accidental shooting while preparing to deploy.
New Caledonia's Pacific neighbours called for a return to dialogue and for the electoral reform to be cancelled.
"These events could have been avoided if the French government had listened," Vanuatu Prime Minister Charlot Salwai said.
The French government says it wants to meet pro- and anti-independence leaders soon in Paris.
It has opened the door to suspending the reform bill if there is a new deal soon on the future of the island.
President Emmanuel Macron cancelled a planned video call with political leaders from the island because leaders did not want to talk to each other, Elysee sources said.
Hinting at foreign interference, Darmanin told France 2 TV "some independence leaders had made a deal with Azerbaijan," a country with whom France's relationship has deteriorated over French support for Armenia.
He gave no evidence, and Azerbaijan's foreign ministry swiftly denied what it called insulting allegations.
Australian Associated Press
