YOKOTA AIR BASE, Japan -- A man who flew a drone carrying radioactive sand onto the roof of the Japanese prime minister's office considered targeting a U.S.-related facility in downtown Tokyo, according to local media.
The unmanned aircraft's operator, Yasuo Yamamoto, 40, reportedly opposed the Japanese government's plans to restart nuclear reactors. He turned himself in to authorities late Friday in Fukui in western Japan, according to The Associated Press.
Posting to an anti-nuclear blog under the name "Kantei (prime minister's office) Santa," Yamamoto wrote that he had checked out areas around the prime minister's official residence looking for a place to launch his drone, according to the Jiji Press news agency.
In November, he wrote that the U.S. may be "an enemy" and that "it is not known if the United States is pressuring Japan to restart nuclear power plants," the agency reported.
Yamamoto also wrote that he scouted a U.S.-related facility in Tokyo's Roppongi entertainment district, "so that I can release it here, not at the prime minister's office, depending on the situation," Jiji Press reported.
Roppongi is flanked by U.S. government facilities, including the U.S. Embassy, the New Sanno Hotel and Hardy Barracks, home to Stars and Stripes' Pacific headquarters and other offices.
U.S. Forces Japan media relations chief Marine Corps Gunnery Sgt. Tiffany Carter said Monday that U.S. officials are aware of the drone incident.
"However, we do not discuss operational security measures at our bases," she said. "We take potential threats to our installations seriously, and recommend all personnel remain ever alert and vigilant."
Base personnel are routinely reminded to maintain their situational awareness and to report any suspicious activity, no matter where it occurs, she said.
U.S. bases in Japan have been targeted by activists in the past. In November 2013 a homemade cannon likely fired "projectiles" at Yokota Air Base, according to U.S. and Japanese officials.
An anti-U.S. military, left-wing extremist group known as Kakurokyo is thought to be responsible for homemade mortar rockets found in November 2009 just outside Yokota and in December 2009 near Naval Air Facility Atsugi.