A French patrol boat opened fire on Melanesian separatists Saturday in the navy's first direct role in violence that has left seven people dead on this island territory.

Twenty-one French police officers were still held hostage in caves on the New Caledonian island of Ouvea. An opposition spokesman demanded that France agree to a referendum on independence.In Paris, the main separatist movement accused the French government of waging a "colonial war" against the native Melanesians.

About 25 military police officers traded gunfire with about 30 armed rebels near a guerrilla encampment at Pouebo, a village on the island's east coast, said Philippe Berges, chief of staff at the French High Commission office here.