Protestors have clashed with Japan's Coast Guard in waters off Okinawa where new runways are to be built for the US Marines.

Locals and envirionmentalists oppose the plan to fill in waters thought to be a habitat for the threatened dugong.

Protestors tried to disrupt work to build a temporary pier in waters off US Camp Schwab.

But their efforts were repelled by ten Japan Coast Guard boats.

Two protestors in a canoe were detained.

Locals also voiced opposition to the plan outside the gates to Camp Schwab.

Protestors scuffled with riot police and attempted to block the transport of building materials into the site.

In the works for years, the plan aims to ease Okinawa's burden by moving functions of the US Futenma air base to a less crowded part of the island.