Japan will sweep regional airports for more unexploded ordnance after a bomb dropped by the United States in World War II blew up on a taxiway in the south, the country's transport minister said Friday.

The 250-kilogram device blew up on Wednesday at Miyazaki airport - a former base for "kamikaze" suicide pilots during the war - shortly after a passenger jet taxied past.

Footage obtained by AFP showed a plume of soil blasting at least 10 metres into the air, with the explosion leaving behind a crater several metres across.

No one was injured but flights were suspended until the evening.

Transport Minister Tetsuo Saito told a briefing on Friday that he had "ordered the magnetic search at Miyazaki airport" and other airports.

The search will initially focus on airports in the regional commercial hubs of Sendai, Fukuoka and Naha, according to national broadcaster NHK.

All once hosted wartime military facilities, local media said.

At Miyazaki, three bombs have been found since 2011, including a one-tonne device discovered during resurfacing work at the airport's parking apron, the Asahi Shimbun reported.

Miyazaki airport originated in 1943 as an imperial Japanese navy base, sending dozens of "kamikaze" aircraft on suicide missions.

Before the nuclear bombings of Nagasaki and Hiroshima in 1945, the US Air Force heavily bombarded dozens of Japanese cities.

Hundreds of thousands of citizens were killed, including around 100,000 in Tokyo on one night in March 1945 alone.

In the year to April 2024, Japan's military safely removed 2,348 unexploded devices, 441 of them in the southern region of Okinawa, according to the Self-Defense Forces.