TOKYO (AP) — Japanese officials say buoys are being floated off the southernmost island of Okinawa in one of the first steps in the relocation of an American military base.

The buoys define the area where the construction will begin on a facility in coastal Henoko that will house the Marine Corps Air Station Futenma, which will be relocated from a crowded residential area of Okinawa.

Okinawa houses the majority of U.S. troops in Japan. Protests against the bases have been going on for decades.

The Japanese Defense Ministry says placing of buoys began Thursday.

The mayor of Nago, where Henoko is located, issued a statement protesting the move. Many people on Okinawa, including Nago’s mayor, want Futenma moved completely off the island.

TV showed protesters on boats being blocked by patrol boats.