It is reported that Viet Nam plans to establish administrative office at Nansha Islands, What is the comment of the Chinese side?

We are seriously concerned with the relevant report and have asked the Viet Namese side to clarify.  China has indisputable sovereignty over Nansha Islands and the adjacent waters.  Any unilateral act by any other country concerning the Islands will constitute an infringement upon China’s territorial sovereignty and will by illegal and null and void.