An unexploded American bomb from World War II that had been buried at a Japanese airport has detonated, causing a large crater in a taxiway and the cancellation of more than 80 flights but no injuries.

Land and Transport Ministry officials said there were no aircraft nearby when the bomb exploded at Miyazaki Airport in south-western Japan.

Officials said an investigation by the Self-Defense Forces and police confirmed that the explosion was caused by a 500-pound US bomb and there was no further danger. They were determining what caused its sudden detonation.

A video recorded by a nearby aviation school showed the blast spewing pieces of asphalt into the air like a fountain.

Videos broadcast on Japanese television showed a crater in the taxiway reportedly about 7 metres in diameter and 1 metre deep.

Chief Cabinet Secretary Yoshimasa Hayashi said the airport hopes to resume operations on Thursday morning.         

Miyazaki Airport was built in 1943 as a former Imperial Japanese Navy flight training field from which some kamikaze pilots took off on suicide attack missions.

A total of 2,348 bombs weighing 37.5 tonnes were disposed of during fiscal year 2023, the Self-Defense Forces have said.

AP/Reuters