The Greens in New Caledonia have denounced last week's arrest of two Kanak leaders who were involved in a roadblock at the Goro nickel project site.
The Nouvelles Caledoniennes newspaper says the Greens issued a statement deploring the police action against Raphael Mapou.
Dozens of people had set up roadblocks last week, accusing the site operators, Inco of Canada, of not respecting the environment.
Customary chiefs and the territorial administration had condemned the action but the Greens say the government and Inco have refused to allow an independent assessment of the environment.
The party has also challenged claims by a chief that the huge project was good for the territory, saying employment opportunities cannot eliminate the risks with the project.