People stage a rally in front of the parliament in Tokyo on May 24, 2015 to protest against a controversial US airbase on Okinawa island, in southern Japan. (AFP)
Thousands of demonstrators formed a human chain around Japan's parliament in Tokyo on Sunday, protesting the planned construction of a new US airbase on the southern island of Okinawa.
The protesters, who organisers said numbered about 15,000, surrounded the parliament building holding banners reading "No to Henoko", in the latest rally against the controversial base.
Henoko is a small coastal area on Okinawa where Tokyo and Washington plan to relocate the existing Futenma military facility, currently situated in built-up Ginowan.
"We must stop this construction," said one of the protesters, Akemi Kitajima, 66.
"The government is trying to force the plan no matter how strongly Okinawa says 'no' to it."
Okinawa is home to more than half of the 47,000 US service personnel stationed in Japan as part of a defence alliance, a proportion many islanders say is too high.
The plan to move Futenma, first mooted in 1996, has become the focus of anger among locals, who insist it should be shuttered and a replacement built elsewhere in Japan or overseas.
But both Tokyo and Washington have repeatedly backed the plan, with Prime Minister Shinzo Abe last month insisting it was "the only solution".
The protestors on Sunday also expressed opposition to Washington's scheduled deployment of CV-22 Osprey aircraft at US Yokota Air Base in Tokyo.
The Osprey is a hybrid aircraft with rotors that allow it to take off like a helicopter and engines that can tilt forward, enabling it to fly like an aeroplane at greater speed than a chopper.
More than two dozen Ospreys have been already deployed at Okinawa's Futenma airbase, prompting safety concerns from local residents.
Sunday's rally comes a week after 35,000 people on Okinawa, led by the anti-base governor, protested the new US base plan.