Emperor of Japan Akihito on Saturday expressed his "deep remorse" over the past war for the first time at an annual national memorial service.

"Reflecting on our past and bearing in mind the feelings of deep remorse over the last war, I earnestly hope that the ravages of war will never be repeated," 81-year-old Akihito said at the memorial service marking the 70th anniversary of Japan's unconditional surrender in WWII.

The soft-spoken emperor has urged Japan not to forget the suffering of the war and tried to promote reconciliation with Asian countries. He has also expressed remorse previously but not at the annual service at Nippon Budokan Hall in Tokyo.

Some media and analysts here believe that a departure from his annual speech may be perceived as a subtle rebuke of Prime Minister Shinzo Abe.

Abe, however, stopped short of mentioning "reflection" at the memorial service for the third consecutive year. In a closely- watched statement released on Friday, the conservative premier reiterated previous governments' apologies over Japan's past wartime actions, but refrained from offering a fresh apology himself.

He also claimed that Japan's future generations must not "be predestined to apologize" for the country's role in the conflict.