Reinforcements sent to quell deadly New Caledonia riots

France hopes to regain full control of events in New Caledonia "in the coming hours", Interior Minister Gerald Darmanin has said, after a third night of riots that have killed four people amid anger over a contested electoral reform.

Rioters have burnt businesses, torched cars and looted shops, and road barricades put up by protesters were causing a "dire situation" for access to medicine and food in the French-ruled Pacific island, authorities said.

France declared a state of emergency in New Caledonia that came into force at 5am on Thursday, and went on to put at least 10 people under house arrest and ban TikTok.

"Sending significant reinforcements, via airlift, will allow for a return to order and guarantee the availability of essential goods on the island," Prime Minister Gabriel Attal said.

Rioting erupted over a new bill, adopted by lawmakers in Paris on Tuesday, that will let French residents who have lived in New Caledonia for 10 years vote in provincial elections - a move some local leaders fear will dilute the Indigenous Kanak vote.

"Everything's burning, people have literally no limits, because they are literally shooting at each other, I've never seen this much violence," said New Caledonia student Olivia Iloa.

Electoral reform is the latest flashpoint in a decades-long tussle over France's role in the mineral-rich southwest Pacific island, which lies some 1500km east of Australia.

French President Emmanuel Macron's government has come under harsh criticism from the opposition and past prime ministers, who say they should not have pressed ahead with the reform.

New Caledonia's Pacific neighbours also called for a return to dialogue and for the reform to be cancelled.

"These events could have been avoided if the French government had listened," said Vanuatu Prime Minister Charlot Salwai, who chairs the Melanesian Spearhead Group that also includes Fiji, Papua New Guinea and Solomon Islands.

New Zealand Foreign Minister Winston Peters said the situation was "of serious concern across the Pacific Islands region".

The French government says it has always been open to dialogue and 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.

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 one in five residents live under the poverty threshold.

The protests were organised by Field Action Co-ordination Cell (CCAT), which was condemned on Thursday by France's High Commissioner Louis Le Franc, who drew a distinction between the organisation and the major pro-independence political party FLNKS, which has called for calm.

Armed forces were protecting New Caledonia's two airports and port, he said, adding that main and secondary roads in Noumea were blocked by barricades of burning cars and car carcasses, some rigged with booby traps.

There were also confrontations overnight between CCAT members and self-defence groups who are also in breach of the curfew and a weapons ban, he said.

Darmanin said numbers of police and gendarmes in New Caledonia would rise from 1700 to 2700 by Friday evening, with a small number of soldiers assisting.

A representative of CCAT said they did not know who was under house arrest.

Three young Kanak have died in the riots, and a 22-year-old police official died after being shot in the head as he was talking to protesters, Darmanin said. Another gendarme died in an accidental shooting while preparing to deploy, the interior ministry said.

Noumea resident Yoan Fleurot said he has seen looting and destruction of property. Some store owners willingly let their shelves be raided, pleading that their shops not be destroyed.

"The truth is that at night you can't even try to go out," he said. "Caledonia will have a hard time recovering from this crisis."