Anti-base protesters took to canoes and boats Tuesday in waters off Okinawa to show their opposition to the planned relocation of a U.S. air base, exactly three years after full-blown offshore landfill work for the transfer began.

Holding signs that read "Stop landfilling operation" and "Protect our beautiful sea," protesters in around 30 canoes paddled out to the site, calling for the halt of work for the transfer of U.S. Marine Corps Air Station Futenma to the Henoko district, both in the southern island prefecture.

Demonstrators in canoes protest against land reclamation work for the planned relocation of U.S. Marine Corps Air Station Futenma in the Henoko coastal area of Nago in Okinawa Prefecture, southern Japan, on Dec. 14, 2021. (Kyodo) ==Kyodo

Frustrated with the noise, crime and accidents linked to the U.S military presence, many local residents remain opposed to the relocation plan as they want the base moved out of the prefecture, which hosts the bulk of U.S. military facilities in Japan.

Under the plan to transfer the functions of the Futenma airfield in a crowded residential area in Ginowan to the new site adjacent to the Marines' Camp Schwab, the central government is scheduled to construct V-shaped runways after reclaiming land in waters off the less densely populated Henoko area in Nago.

During the demonstration, around 20 canoes breached the containment boom that divided the landfilling area from the ocean, prompting Japan Coast Guard officials on duty to rush out to block them and causing a brief scuffle.

Protesters yelled in chorus "Stop illegal construction" and "Don't kill the coral," as sand-carrying ships and dump trucks came and went from the area.

Some of the protesters also gathered in front of a gate of the Camp Schwab.

Chief Cabinet Secretary Hirokazu Matsuno stressed the central government's position in a press conference on Monday, saying the Futenma base relocation to Henoko is "the only solution."

A Japan Coast Guard officer (L) confronts a demonstrator in a canoe who is protesting against land reclamation work for the planned relocation of U.S. Marine Corps Air Station Futenma in the Henoko coastal area of Nago in Okinawa Prefecture, southern Japan, on Dec. 14, 2021. (Kyodo) ==Kyodo

Okinawa Prefecture led by anti-base Gov. Denny Tamaki has been in a legal battle with the central government over the base relocation issue, but many courts have ruled in favor of the state.

In November this year, Tamaki refused to accept the central government's planned design change for the Futenma base relocation to address weak ground found earlier in the planned reclamation area, hindering the construction process and likely triggering a fresh legal battle.

Even if the design change is accepted, it is still expected to be at least another 12 years before the new base is fully operational.

The relocation plan dates back to a 1996 Japan-U.S. accord on the return of the land occupied by the Futenma base, struck amid public outrage over the 1995 gang rape of a 12-year-old schoolgirl in Okinawa by three U.S. servicemen.