Trainee jet pilot shoots up car park.
There were no injuries, but Japan's defence ministry immediately apologised and suspended all air defence force training which involves shooting.
The shattered car was parked at a drug addiction rehabilitation centre near an air defence force practice firing range, on the northern island of Hokkaido.
The roof of a minibus garage at the centre had a hole in it, but bullets did not hit the bus inside.
'This sort of incident should never happen. I would like to apologise,' said vice defence minister Ken Sato. 'This is unbelievable.'
The ministry sent investigators to Hokkaido to question the fighter pilot. A rehabilitation centre spokesman said: 'We were so fortunate it happened just before lunch time when almost everyone was inside the building.'
The defence ministry said 200 rounds were fired, but only 18 were had been recovered.
Another report said bullet traces were also found at a golf course near the training grounds. A ministry spokesman said it was possible some rounds hit one of six golf courses around the training site.
Tomoko Tanaka, a spokeswoman for Japan's Air Self-Defence Force, said the 20mm practice machine gun rounds were fired inadvertently.
She said the F-4 fighter, with a two-person crew, was conducting an air-to-ground firing drill.