Japan must say it's sorry repeatedly to China and the other countries it invaded in the 20th century until its former victims have heard the apology enough times, according to novelist Haruki Murakami.

"The issue of historical understanding carries great significance, and I believe it is important that Japan makes straightforward apologies," he told Kyodo News in an interview in Tokyo.

"I think that is all Japan can do - apologize until the countries say, 'We don't necessarily get over it completely, but you have apologized enough. All right, let's leave it now'."