The Tongan government has finished installing a navigation beacon on the disputed Minerva Reef, south of Tonga and Fiji.
Both countries claim ownership of the atolls.
Workers from Tonga's Defence and Works and Transport Ministries have spent two weeks putting up the beacon on the Teleki Tonga Reef.
Another beacon was installed at Teleki Tokelau Reef last year.
Last year, Tonga accused the Fiji military of damaging the two beacons.
Tonga has claimed ownership since 1972, but Fiji says the reef falls within its Exclusive Economic Zone which is registered with the UN.
Tonga has paid 224,000 US dollars to reinstall the beacons.