A prominent activist in Okinawa pleaded not guilty on Friday to charges of forcible obstruction of a business and assault in connection with his opposition to U.S. bases in the prefecture.

During his first hearing before the Naha District Court, 64-year-old Hiroji Yamashiro, head of the Okinawa Peace Action Center, admitted to the charge of property destruction for cutting barbed wire at a base.

Yamashiro, who has led groups objecting to the relocation of U.S. Marine Corps Air Station Futenma within the prefecture, has remained in detention for five months since his arrest in October, prompting human rights groups, including Amnesty International Japan, to call for his immediate release.