Akihito in hospital

Japan's Emperor Akihito arrived at this Tokyo hospital to be greeted by medical staff and a mass of waiting media.

The 78-year-old is due to undergo a five-hour coronary by-pass operation on Saturday.

He's been treated for heart problems for the past year.

The Emperor gained a huge popularity boost when he visited areas of Japan hit by last year's quake and tsunami within days of the disaster.

Well-wishers at the University of Tokyo hospital where Akihito was admitted on Friday said they were hoping for the best.

SOUNDBITE: Suhara Kageyama, well-wisher, saying (Japanese):

"I hope the Emperor will hang on. If the Emperor can recover then it would improve the spirits of the whole country, especially in Tokohu."

SOUNDBITE: Shizue Baba, well-wisher, saying (Japanese):

"From the bottom of my heart I pray that he will make a complete recovery, and it's for that reason I came here today."

A tent with a book for well-wishers to leave messages has been set up at the hospital.

It'll be there until the Emperor's doctors allow him to leave, expected to be in about two weeks time.

Paul Chapman, Reuters