Arsonists torched schools and hundreds of cars overnight in New Caledonia, officials said on Wednesday, as French President Emmanuel Macron embarked on a surprise visit aiming to end nine days of deadly riots on the French Pacific archipelago.

Macron left Paris on Tuesday on a flight to the troubled territory, a popular holiday destination where roads are now littered with charred vehicles, and scores of shops, schools and other buildings are in cinders.

Clashes have left six people dead and hundreds injured since unrest erupted on May 13 on the Pacific islands, home to 270,000 people.

French authorities said the violence had eased since 1,050 troops, tactical police and national security reinforcements from Paris were deployed, including to "highly sensitive" areas.

Nevertheless, two primary schools and 300 cars in a dealership were torched in the territory's capital Noumea during the night, the mayor's office said.

The deadliest unrest in four decades has been blamed on French plans to give voting rights to thousands of non-indigenous residents, which Indigenous Kanaks say will dilute their votes.

An official close to the president said Macron aims to "listen to, talk and hold discussions with New Caledonian elected officials" in an attempt to restore order.

He wants to "give answers to the many legitimate questions Caledonians are asking, both on the reconstruction side and the political side", the official added.

But one Kanak manning an unofficial roadblock north of the capital Noumea said Macron needed to understand Indigenous opposition to the vote reform.

"I don't know why our fate is being discussed by people who don't even live here," said the 52-year-old, who gave only his first name Mike. (AFP)