The Defense Ministry on Tuesday began the first of its full-scale U.S. base relocation work on the Oura Bay side of the Henoko coastal area in the city of Nago, Okinawa Prefecture.

The work, which involves constructing seawalls on the Oura Bay side with soft ground, is part of the project to build a replacement facility for the U.S. Marine Corps' Futenma air station in the city of Ginowan in the prefecture. The ministry plans to fill in the area surrounded by the seawalls with soil.

Meanwhile, the Okinawa prefectural government is demanding that the Oura Bay work be halted, claiming that the ministry has not completed its prior consultation with the prefecture.

On Tuesday, metal stakes were driven into the seabed, as protesters rallied around the site.

In December last year, following the discovery of the soft ground on the Oura Bay side, land minister Tetsuo Saito gave proxy approval for a design change to the base relocation project, after Okinawa Gov. Denny Tamaki refused to approve the change.

The ministry's Okinawa Defense Bureau then notified the prefectural government in June that it would end prior consultation with the prefecture side and launch the full-scale Oura Bay work as early as Aug. 1.