Interest rates are on the way up, Bank of Japan Gov. Toshihiko Fukui said Friday in testimony to a House of Representatives committee on financial and monetary matters.

"It will become necessary, eventually, to raise interest rates in phases," he said, adding that "the function of interest rates can be best fulfilled if they are set at a level that is most appropriate for the prevailing economic and price trends."

But Fukui also sounded a note of caution, indicating the timing of any future rate increase needs to be studied carefully.