The recent discovery of a drone on the rooftop of the Prime Minister's Office in Chiyoda Ward, Tokyo, appears to reveal holes in the security measures implemented in and around the building and other important facilities in that area.
A suspect arrested in the case also attempted to sneak the remotely piloted aircraft into airspace over a nuclear power plant in Kagoshima Prefecture in October, his online blog shows.
On April 22, when the drone was found on the rooftop, Yasuo Yamamoto, 40, posted messages on his blog appearing to ridicule personnel in charge of patrolling in and around the Prime Minister's Office.
"It's been too slow," the suspect wrote. "[The drone] was left alone [on the rooftop] for two weeks!"
Yamamoto lives in Obama, Fukui Prefecture, and was later arrested by the Metropolitan Police Department.
According to his statements to the police, Yamamoto flew the drone toward the Prime Minister's Office on April 9 from a parking area in the Akasaka district of Minato Ward, located about 200 meters from the building.
If true, the drone was undetected for nearly two weeks. An MPD official said with a pained expression: "It was an unforgivable failure by the security authorities. We have to accept whatever will be said of us."
The Prime Minister's Office is guarded by the MPD's team in charge of security of the building, MPD mobile units and Kojimachi Police Station. Police officers watch the gates to the building and areas around the building's premises 24 hours a day.
The inside of the premises is guarded by the building's administration office. That includes the rooftop, but it was not covered by regular patrols.
Yamamoto's blog contains details of developments until the revelation of the drone incident. He flew the drone at about 3:30 a.m. on April 9 after going to the Akasaka district, controlling it in the parking area, which is surrounded by buildings.
He changed to that location from another place because the Akasaka district and nearby areas were full of taxis waiting for passengers. He initially planned to fly the drone before dawn on April 8, but gave up due to strong rain and wind.
According to his blog, Yamamoto waited for an opportunity while hiding from police officers patrolling on bicycles, who passed by him about every hour.
Highly important facilities are concentrated in the Akasaka district and nearby. They include the Diet Building and the US Embassy, in addition to the Prime Minister's Office. The Akasaka district is one of the most heavily guarded places in central Tokyo, but Yamamoto was not caught by the security networks.
According to his blog, Yamamoto attempted to send the drone into the premises of nuclear power plants before flying it to the Prime Minister's Office building. In October last year, Yamamoto tried to fly the drone into the premises of Kyushu Electric Power Co.'s Satsumasendai nuclear power plant in Sendai, Kagoshima Prefecture.
He looked at photos of areas around the nuclear power plant in advance on the Google Map Internet mapping service, to confirm the heights of fences and conditions of barbed wires.
Around Oct. 2 last year, Yamamoto drove to the Sendai plant, which is nearly 1,000 kilometers from Obama. He spent a day there, controlling the drone in an attempt to "spy upon" reactor buildings of the nuclear power plant.
His plan failed, however, because the distance was too far for the drone to transmit photo images. He continued to watch areas around the nuclear power plant. His blog said that he was spotted twice by a car that was apparently a police vehicle.
Yamamoto wrote on this blog: "Is that police? Then I was being watched."
He then travelled to the Genkai nuclear power plant in Genkai, Saga Prefecture, where he photographed fences of the plant and indicated his intention to send the drone into its premises.
According to Kyushu Electric Power Co., there are no restrictions on shooting photos or videos from outside the nuclear power plant's premises.
Last summer, the company confirmed that a video clip of the nuclear power plant had been posted on the video-sharing website YouTube. The video clip was apparently shot by a drone from air space outside the premises of the plant.
On alert for reconnaissance
By Masatoshi Imai / Yomiuri Shimbun Staff Writer
The Prime Minister's Office and nuclear power plants are among key facilities that need special protection by the police. The authorities call them "important protection facilities."
On Wednesday, when a drone was found on the roof of the Prime Minister's Office, the National Police Agency instructed prefectural police headquarters across the nation to strengthen their surveillance over surrounding areas and airspace around important protection facilities. They also were told to examine ways to take shelter in case they find drones that appear dangerous, such as those mounted with explosives.
Under the safety standards at nuclear power plants formulated by the Nuclear Regulatory Authority, measures to deal with the possibility of an airplane crashing into a nuclear power station are required. A government official in charge said, "Even if a drone mounted with a small bomb crashed into a nuclear reactor building, it would not seriously damage the containment vessel."
More alarming would be "a drone used for reconnaissance by terrorists," according to a senior NPA official.