TOKYO, April 23 (Xinhua) -- Protestors in Japan's southernmost prefecture of Okinawa staged a sit-in rally on Monday to show their objection to the planned transfer of a controversial U.S. air base within the prefecture.

The protest comes one year after the central government started building seawalls as one of the first steps of building the new base, which will see the functions of the U.S. Marine Corps Air Station Futenma in densely-populated Naha transferred to the coastal Henoko region also on the island.

But locals and officials in Okinawa want to see their decades-long base-hosting burdens lifted by some, if not all, of the U.S. bases being relocated outside the prefecture, or out of Japan entirely.

Okinawa Governor Takeshi Onaga, a staunch proponent of lessening the U.S. base-hosting burdens of Okinawa, has mounted a series of legal campaigns against the central government to block the relocation move.

Sources close to the matter believe that along with environmental concerns, Onaga may seek to retract approval given for the landfill work by his predecessor, in a further bid to scupper the central government's plans.

The prefectural government believes that fishing rights have been granted in the Henoko region, meaning the central government's construction work is infringing on the rights of local fisherman.

Legal action has also been taken based on the premise that the construction work will irrecoverably damage the region's delicate ecosystem by crushing rocks as part of the land reclamation work.

Prefectural opponents to the construction work have expressed their fears that sediment being poured inside the seawalls being constructed for the replacement facility in Oura Bay, will be extremely detrimental to the environment.

The nationwide liaison council Opposition to Henoko Soil Hauling in a study meeting concurred that not only does the central government's reclamation work go against the National Biodiversity Strategy of Japan, it is also disrupting an ecosystem unique only to Okinawa.

Furthermore, the local Anti-Helicopter Base Council Diving Team Rainbow, having surveyed the coral reef at the bottom of the ocean near the tip of one of the seawalls, concluded that the Porites lutea coral, which is part of the reef and just 20 meters away from the tip of the seawall, has a high likelihood of being destroyed by rocks being thrown into the ocean due to the construction.

One of the representatives of the team said that after photographing the coral reef it was clear that if the seawall construction continues then the coral and the fish in the region will be wiped out.

The waters of Oura Bay are also the last home of the endangered Japanese dugong, which is a large marine mammal and cousin of the manatee. Environmentalists are certain of the species' extinction if the central government's construction continues.

The return of the land to Okinawa used for the Futenma base was agreed in 1996 between the United States and Japan and in 2006 both sides inked a deal, part of which included transferring the airfield to the Henoko region on the island.

Vehement opposition from local officials and residents of Okinawa to the base move, which hosts 74 percent of all U.S. bases in Japan, has also fueled an overall anti-U.S. sentiment on the tiny island in the wake of a number of heinous crimes committed by U.S. base-linked personnel.

More than 300 people were involved in the protest on Monday which is slated to last for six days through Saturday.

As well as residents from the local area near Camp Schwab in Henoko where the protest took place, people from around Okinawa as well as from Japan's mainland and lawmakers from the island also took part in the demonstration, local media reports said Monday.

One female member of the demonstration in her 60s shouted Monday that it was time for the U.S. military to "leave us alone" and that all U.S. bases should be "moved out of Japan!"

Another in her 70s said they will do "whatever it takes" to disrupt the construction work of the new base and "nothing would stop their will."

"We will sit here for as long as it takes. Enough is enough!" a man in his 40s shouted.

However, the central government has consistently maintained that shifting the base to Henoko on the tiny subtropical island remains "the only solution."