TOKYO, Feb 18, 2012 (AFP) - Japan Emperor Akihito's heart bypass surgery that lasted about five hours ended successfully Saturday, national network 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) and the surgery lasted more than five hours.

The aim of the procedure was "to maintain and to improve his majesty's daily life", a palace spokesman said earlier.