A massive fire devastated a historic castle on the southern island of Okinawa in the early hours of Thursday and destroyed large parts of the world Heritage site’s complex, according to local authorities.

The Shuri Castle is a key part of a complex dating back to the Ryukyu Kingdom and is believed to have been in use from around the 1400s. Most of the current structures are reconstructions based on original plans and photos of the old castle.

There were no initial reports of injuries, but nearby residents were evacuated while firefighters spent several hours attempting to bring the fire under control.

Recently, the castle has come to symbolise Okinawa’s struggle to overcome the devastation of war. More than 200,000 Americans and Japanese, including around a quarter of Okinawa’s civilian population, died during a fierce 82-day battle from April to June 1945. The island is still home to a large number of US military bases.

Ryo Kochi, a spokesman with the Okinawa prefectural police said, “The cause of the fire has not been determined yet but a security company alarm went off at around 2.30 in the morning”.

“All the (three) main buildings have burnt down, with nothing left behind,” Daisuke Furugen, an official with the local Naha fire department, told AFP.

The blaze started before 3:00 am on Thursday morning, with the cause unknown as yet.

It started in the elaborate main building of the complex, a grand red structure with traditional tiling on the roof, and spread quickly to nearby buildings, officials said.

Television footage showed large orange flames engulfing the castle before sunrise, with daylight revealing the extensive damage done to the site. In some cases, little more than charred and smoking wood was left behind.

Japan is dotted with historic castle complexes, most of which are careful reconstructions of original buildings.

Unesco was particularly impressed by the reconstructed main hall of the Shuri castle, describing it as “a great monument symbolising the pride of the Ryukyu people”.

(With inputs from agency)