Two projectiles were fired at the U.S. Air Force Yokota base in western Tokyo late Wednesday night in what police believe was an attack by extremists opposing a possible war on Iraq.
No injuries were reported. Authorities said they have not found the projectiles, which were apparently fired from an automatic launcher.
Police said they received an emergency call at around 11 p.m. that bright objects were seen flying near the east gate of the base.
Two smoldering metal pipes equipped with what appeared to be timing devices were later found at a construction material storage site about 300 meters west of the base, police said.
According to the Tokyo Fire Department, residents on the southwestern side of the base reported hearing two explosions.
A 43-year-old woman living near the storage site in Fussa said she heard two consecutive loud explosions and the blast rattled her house.
"Initially, I thought it was traffic accident," she said.
The incident came one day after authorities found an apparent projectile launcher in Chiyoda Ward that had apparently been aimed at the Defense Agency.
Because the launchers in both cases were similar, police said the same party may be involved.
The Yokota base was the target of an extremist attack in July 2000 prior to the Group of Eight summit in Okinawa. In that incident, a metal projectile was fired from a material storage site 300 meters outside the base.