Aomori Gov. Shingo Mimura lodged a protest Thursday with Defense Agency Director General Fukushiro Nukaga over Tuesday's accidental firing of live ammunition toward land by a Maritime Self-Defense Force ship docked in the prefecture.

"The accident could have endangered the lives of nearby residents," he told the agency chief. "This sort of thing must not happen."

The 50-ton Misairutei San Gou (Missile Ship No. 3), a missile-armed hydrofoil docked at MSDF Ominato Regional District Headquarters, accidentally fired 10 20-mm rounds of live machine gun ammo toward land at around 7:20 p.m. Tuesday, hitting trees. No injuries were reported.

"I thought all the bullets were exhausted during a drill so that the machine gun was empty," the MSDF member in charge of firing at the time was quoted as telling headquarters.

The incident occurred after the vessel returned to base after a shooting drill in the Sea of Japan because a remote control for the machine guns failed, the Defense Agency said.

MSDF safety regulations require machine guns to be checked for bullets after live-ammunition drills.

The MSDF is investigating the incident.

Mimura also told Nukaga to take preventive measures by determining the cause of the incident and fully checking the equipment.

Meanwhile, Defense Agency Vice Minister Takemasa Moriya told reporters, "This is something we should never have let happen. If people blame us for a lack of seriousness, we have to accept it."