The general secretary of the Caledonian Union has been suspended over unspecified wrongdoing.
According to local television, New Caledonia's leading pro-independence party took the measure against Philippe Ajapuhnya for what the party described as an incident of extreme seriousness.
Media reports said the issue related to events in Koutio last Saturday night.
No details were given by either the police or the party but reports said Mr Ajapuhnya was taken into custody.
The party said it acted swiftly as not to tarnish the movement's reputation.
It said it would discuss the issue when its leadership met on Monday.