New Caledonia's USTKE union has blocked about 30 businesses in the Noumea area as part of what it calls a general strike.
The action has been taken in response to employers taking measures against union members joining in previous stoppages.
One unionist says the action is being taken to push for their right to strike which he says is a constitutional right.
He says until proven to the contrary, they are still French citizens.
The employers organisation has denounced the strike affecting about 2,000 employees as unacceptable.
The latest action comes as USTKE members face jail terms over clashes in January when unionists refused to disperse from publicly owned land next to the bus depot at the centre of their industrial action.
About 30 people, including police officers, were injured.