Bank of Japan Deputy Governor Masayoshi Amamiya said the central bank could widen the band in which it allows bond yields to fluctuate around its 0% target, if long-term interest rates make big swings.

"It's true we could be more careful in assessing the merits and demerits of additional action than other central banks," Amamiya told a news conference after meeting with business leaders.

"But just because we've eased so much already does not mean any further steps would be limited or small." Amamiya added.