TOKYO - Japan Emperor Akihito's heart bypass surgery that lasted more than five hours ended successfully Saturday, national broadcaster NHK and other media said.
The 78-year-old emperor was advised to undergo the procedure after tests showed a narrowing of two of his coronary arteries.
The Imperial Household Agency declined to immediately confirm the reports of the successful operation.
His doctors were scheduled to hold a press conference from 6:00 pm (0900 GMT).
The emperor went into the operating theatre at the University of Tokyo Hospital at 9:24 am (0024 GMT). The surgery, which was performed by a team of physicians from the hospital and the private Juntendo University, lasted over five hours.
The aim of the procedure was "to maintain and to improve his majesty's daily life", a palace spokesman said earlier.
The monarch arrived at the hospital on Friday morning accompanied by his wife Empress Michiko, while thousands of members of the public visited the Imperial Palace to sign books wishing him well.
The emperor is likely to be discharged after about two weeks if he recovers well from the operation, Jiji Press earlier reported.
Despite being stripped of much of its mystique and its quasi-divine status in the aftermath of World War II, the Japanese throne is held in deep respect by much of the public.