An expert in the Law of the Sea says Tonga's re-erection of navigational beacons on the Minerva Reefs is a way of stating its claim over the disputed area.
Fiji and Tonga both claim the reefs and the area's been the focus of escalating tension between the two countries.
Tonga says the beacons were destroyed by the Fijian military.
Dean of Law at the University of Western Australia, Professor Stuart Kaye, says their re-construction is significant not just for shipping safety.
"They also indicate sovereignty. if you have a beacon of that type and you put it up and it goes unchallenged, it's very difficult for another state to say it's not your territory and this has probably motivated the Fijians to destroy the beacon and the Tongans to re-construct it."
Dean of Law at the University of Western Australia, Professor Stuart Kaye.