"It's true that Japan's economy is currently in a severe state, mainly due to the slowdown in overseas growth. I would like to carefully scrutinise what downside risks could materialise," Shirai told a news conference after a meeting with business leaders in Kumamoto, southern Japan.

Earlier, speaking to business leaders, she warned of looming risks to the economic outlook that could keep price growth lower than the central bank's forecasts, keeping alive market expectations of further monetary loosening as early as this month.

The former IMF economist has voted with the majority since joining the board in April last year. She is considered to be among the more pessimistic board members on Japan's economic outlook.

The BOJ set a 1 percent inflation target in February and has eased monetary policy four times so far this year to beat deflation and ease the pain on the export-reliant economy from a strong yen and weakening global demand.