Okinawa - The US has begun relocating thousands of Marines from the island of Okinawa, Tokyo and Washington said Saturday, after decades of mounting grievances among locals over the American military presence.

In 2012, the US said it would redeploy 9,000 Marines from the island, where communities say the bases have caused serious disturbances, including pollution, noise, and helicopter crashes.

The relocation began with "a small detachment of approximately 100 logistics support Marines" transferred to the US-occupied island territory of Guam, Japan's defense ministry and the US Marine Corps said.

"Commencement of relocation to Guam signifies the first phase of relocating Marines to locations outside of Japan," said the joint statement.

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There are currently around 19,000 Marines in Okinawa – located east of Taiwan, which has become a flashpoint for tensions between the US and China.

Beijing claims Taiwan as part of its territory, while Washington is Taiwan's biggest supplier of arms.

The 9,000 relocating Marines are set to be moved elsewhere in the Pacific – to Guam, Hawaii, or Australia, the US has said.

Okinawa – formerly under US occupation – today hosts more than half of the 50,000 American troops posted in Japan.

The 1995 gang rape of a 12-year-old girl by three US soldiers in Okinawa also prompted widespread backlash, with calls for a rethink of the 1960 pact allowing the US to post soldiers in Japan. Rape allegations have continued in the years since.

Some Okinawa peace activists argue that their homeland is occupied by both the US and Japan and are fighting for restoration of independence and the removal of troops from both countries.