Japan's Emperor Akihito will break with a centuries-old burial tradition by opting to be cremated like most ordinary citizens in the densely populated nation, officials said Friday.

That would mark the first time in almost 400 years that a Japanese emperor has not been buried, according to the Imperial Household Agency.

It added that the 79-year-old emperor's wife, Empress Michiko, would also be cremated.

The agency, which runs the affairs of Japan's revered imperial family, said the couple were concerned about limited space in Tokyo's royal graveyard.

"Cremation has become a common practice in Japan and imperial history has seen both cremations and burial," the palace said in a statement.

Cremation is common in the country of 128 million people, where space is at a premium, while it is also a frequent practice in Buddhism.

The imperial couple's remains would be placed into a pair of relatively modest, yet-to-be-constructed tombs in the graveyard where wartime Emperor Showa, his father Emperor Taisho and their wives were buried.

AFP