Photo/IllutrationPolice seal off the area where a drone was found crashed on the rooftop of the prime minister’s office in April 2015. (Asahi Shimbun file photo)

The head of the Pacific Command for U.S. forces called on Tokyo to regulate drone flights over U.S. military installations in Japan before a "dangerous" incident, such as an accident or terrorist attack, occurs.

Hawaii-based Adm. Harry Harris made the request during talks in November with Defense Minister Itsunori Onodera in Tokyo, sources said.

Japanese government officials said Harris asked Onodera to plug legal loopholes to prevent drones from flying over U.S. military installations.

In response, the government has started work to revise related laws and regulations, the officials added.

Harris pointed out during the Nov. 16 meeting at the Defense Ministry that drones frequently buzz the U.S. Marine Corps Camp Schwab in Okinawa Prefecture.

He called it a potentially very dangerous situation, given the possibility that a drone could collide with U.S. military aircraft.

He asked Onodera to take immediate action, and repeated the request when he visited the prime minister’s office to meet with a high-ranking official there.

Of key concern appears to be the potential for drones to be used in a terrorist attack targeting U.S. military bases.

“The U.S. forces have a strong recognition that drones are weapons for attacks as well as for reconnaissance," said a high-ranking official of the Japanese Self-Defense Forces. "For a long time, U.S. forces have been extremely worried about the fact that drones are able to fly freely over U.S. military bases in Japan.”

A number of incidents, such as one in which a drone was found on the roof of the prime minister's office in April 2015 after apparently crashing, led the government to revise provisions in the Aviation Law with regard to drones. The revised bill passed the Diet in September of that year.

It prohibits people or organizations from flying drones over areas around airports, densely populated areas and airspace at the altitude of 150 meters or higher from the ground or water surface unless they have permission.

However, the stipulations of the revised law do not apply to U.S. military facilities.

This means it is legal to operate drones over the airspace at U.S. military facilities at altitudes lower than 150 meters.

In March 2016, the Diet passed the drone regulation law that prohibited drone flights over important facilities, such as the prime minister’s office, the Diet building, the Imperial Palace, nuclear power plants and foreign embassies, without permission.

However, the law does not regulate drone flights over U.S. military facilities on a regular basis.