Thousands of residents in the western city of Iwakuni protested in the rain Sunday against the expansion of a US Marine Corps base, DPA reported.
Organizers said about 5,000 people participated in the protest as the US military was planning to begin daily operations on a new aircraft runway built in the city.
"Despite a change of government, the relocation plan for the city's US military base has not been reviewed. The government approved the plan, ignoring the wishes of Iwakuni citizens," said Katsusuke Ihara, a former mayor who organized the protest.
Residents opposed a 2006 US military realignment plan to transfer American aircraft carriers from the US military base in Atsugi near Tokyo to Iwakuni, 900 kilometres west of the capital.
Prime Minister Yukio Hatoyama's Democratic Party of Japan won a landslide victory in August, ending more than a half-century of almost uninterrupted rule by the Liberal Democratic Party.
Iwakuni citizens said the government had not provided them with detailed information and explanations about the military plans.
Mizuho Okada, a 17-year-old high school student who spoke to the crowd, said she and her classmates often could not hear their teacher because of the noise from the US military base.
"I would like to complain to the US about the noise," she said, and also implored her neighbours to consider the next generations.
"I would like to ask adults: Are you participating in politics, thinking about the future of young people?"
Japan's central government spent more than 200 billion yen (22 billion dollars) on the project.
"The expansion has caused local outcry but has not raised the same controversy as the proposed relocation of Marine Corps Air Station Futenma on Okinawa," Stars and Stripes, the US military's newspaper, reported in mid-April, referring to the Iwakuni base expansion.
The article angered local residents, the majority of whom had voted against the relocation plan twice in non-binding referendums.
One month ago, 90,000 people rallied in Okinawa against plans to build a new military base on northern part of the island to replace the controversial Futenma station surrounded by residential areas and schools. Okinawa lies 1,600 kilometres south-west of Tokyo.
Despite his election promise to move the proposed facility off Okinawa, Hatoyama, who visited the island Sunday once again, has backpedalled, asking the island to accept it.