The presumed ringleaders of the unrest in New Caledonia have been placed in home detention and the social network TikTok has been banned as French security forces struggle to restore law and order.

The French territory faced its fourth day of severe unrest on Thursday after protests erupted over proposed constitutional amendments.

Four people have now been confirmed dead, Charles Wea, a spokesperson for international relations for the president's office, said.

A newly introduced state of emergency has allowed presumed ringleaders to be placed in home detention, as well as a ban on Tiktok to be put in place.

French High commissioner Louis Le Franc said Nouméa remained the hottest spot with some 3000-4000 rioters still in action on the streets of the capital Nouméa and another 5000 in the Greater Nouméa area.

Wea told RNZ Pacific the demonstrators "were very angry when their friends and families have been killed".

"Shops are still closed. Many houses have been burnt. The international airport is closed, only military planes are allowed to land from Paris."

Reports RNZ Pacific is receiving from the capital paint a dire picture. Shops are running out of food and hospitals are calling for blood donations.

"This morning (Thursday, local time) a few shops have been opened so people can buy some food to eat," Wea said.

RNZ Pacific former news editor Walter Zweifel, who has been covering the French Pacific territory for over three decades, said New Caledonia had not seen unrest like this since the 1980s.

The number of guns circulating in the community was a major problem as people continued to carry firearms despite a government ban, he said.

"There are so many firearms in circulation, attempts to limit the number of weapons have been made over the years unsuccessfully.

"We are talking about roughly 100,000 arms or rifles in circulation in New Caledonia with a population of less than 300,000."

One of the four people dead was a French gendarme, who was reported to have been shot in the head.

"The other three are all Melanesians," Le Franc said.

One was a 36-year-old man, one was a 20-year-old man and one was a 17-year-old girl.

The deaths occurred during a clash with one of the newly formed "civil defence" groups, who were carrying guns, Le Franc said.

"Those who have committed these crimes are assassins. They are individuals who have used firearms.

"Maintaining law and order is a matter for professionals, police and gendarmes."

Le Franc added: "We will look for them and we will find them anyway, so I'm calling them to surrender right now... so that justice can take its course."

'Mafia-like, violent organisation'

French Home Affairs and Overseas minister Gérald Darmanin told public TV channel France 2 he had placed 10 leaders of the CCAT (an organisation linked to the pro-independence FLNKS movement and who Darmanin believed to be the main organiser of the riots) under home detention.

"This is a Mafia-like body which I do not amalgamate with political pro-independence parties...[CCAT] is a group that claims itself to be pro-independence and commits looting, murders and violence," he said.

Similar measures would be taken against other presumed leaders over the course of Thursday (French time).

"I have numerous elements which show this is a Mafia-like, violent organisation that loots stores and shoots real bullets at (French) gendarmes, sets businesses on fire and attacks even pro-independence institutions." Darmanin told France 2.

Massive reinforcements were to arrive shortly and the French state would "totally regain control", he said.

The number of police and gendarmes on the ground would rise from 1700 to 2700 by Friday night.

Darmanin also said that he would request that all legitimate political party leaders across the local spectrum be placed under the protection of police or special intervention group members.

• RNZ