The government on Wednesday started construction work for the transfer of a key U.S. military base within Okinawa Prefecture after overriding the local government's objection and approving a modified landfill plan by proxy — an unprecedented move.

The work is to reinforce soft ground at the relocation site for U.S. Marine Corps Air Station Futenma and is projected to take nine years and three months, Chief Cabinet Secretary Yoshimasa Hayashi told a regular news conference in Tokyo.

Shortly after noon, the central government began embedding stones into waters on the Oura Bay side of the coastal Henoko area in Nago, Okinawa Island, the Defense Ministry said. The area is to be reclaimed for the base construction.