Thousands of people surrounded Japan's parliament on Sunday to protest against government plans to relocate a US military base on Okinawa island, local media reported.
Kyodo news agency said some 28,000 protesters had ringed parliament house in central Tokyo, holding hands and shouting: "Don't build the base!"
Hundreds more held similar protests across the country, it also reported.
Okinawa was the site of Japan's only land battles in World War Two and many residents there resent the fact that it hosts tens of thousands of US troops and military.
The United States and Japan agreed in 1996 to relocate the base, currently in a heavily populated area, to a new site in Henoko, but many residents of the island have rejected the proposal and want the base moved altogether.
Many residents of Okinawa say they associate US bases with noise, pollution and crime.