Public prosecutor Claire Lanet told local radio the policeman was injured when a shot was fired directly at a vehicle in Mont Dore near the capital Noumea during attempts to put out a roadside fire last night.
The officer was transferred to Gaston Bourret Hospital and the prosecutor says legal proceedings are underway.
Yesterday, a key road into New Caledonia's capital was blocked after truck drivers attached to nickel mining contractors staged another protest over nickel exports to China.
It follows unrest and fires broke that out close to the southern town of Mt Dore which was effectively blocked by protesting groups along with other roads in to nearby Noumea.
Ground reports indicate the unrest is a sequel to a protest by truck drivers about the territory's mining policy two weeks ago.
They want New Caledonia's government to begin exporting ore to China after a fall in exports to South Korea, Japan and Australia.
The contractors who transport the ore from the mine to the port, require the opening of a new export channel to China, as the only way to maintain their activity during the downturn.
New Caledonia's President, Philippe Germain, has said that opening up exports to China "is a question relating to the Nickel strategy, and can only be dealt with after much more detailed discussion and debate."