A fire has destroyed much of Shuri Castle, a World Heritage site on Japan's southern island of Okinawa, with its main hall reduced to a skeleton.

Television footage showed firefighters still battling flames at the multi-structured, wooden castle this morning. Emergency responders received the first call about the fire around 2.47am (1.47am in Malaysia), public broadcaster NHK said

A popular tourist attraction, Shuri was built more than 500 years ago as the royal castle of the Ryukyu Kingdom.

The fire tore through the castle in the middle of its annual mid-autumn festival. It had been scheduled to be included as a stop on the 2020 Tokyo Olympic torch relay route.

Located on a hilltop overlooking the city of Naha and enclosed by curved stone walls, the castle and its surrounding structures were painted a vivid red, and recognisable by their sloped tiled roofs.

It has been destroyed and rebuilt after many fires - most recently in the Battle of Okinawa in 1945.

After World War II, the castle served as a campus for Okinawa's largest public university until the mid-1970s. Following a restoration, the castle re-opened as a national park in 1992. It was designated a World Heritage site in 2000.

In addition to the main hall, the north and south halls have been destroyed, NHK said.

- Reuters