The Japanese government has approved, in place of the prefectural government, ground improvement work as part of a project to relocate a US Marine base in Okinawa Prefecture.

The central government plans to relocate the US Marine Corps Futenma Air Station from densely populated Ginowan City to a site at Henoko, Nago City, despite the opposition of the Okinawa government.

Okinawa officials have defied a high court ruling ordering the prefecture to approve related ground improvement work at the offshore site by Monday.

The land ministry gave the green light to the work on Thursday morning. It is the first time for the central government to override a decision by local authorities based on the local autonomy law.

Following the approval, the Defense Ministry plans to start ground improvement work at the relocation site in mid-January.

Okinawa Governor Tamaki Denny told reporters on Thursday that the central government's decision violates the autonomy and self-reliance of regional governments.

He said he believes Okinawa must once again let it be known that this is not just a problem concerning the prefecture.