Some members of the Bank of Japan's board voiced concern that tweaking its ultraeasy monetary policy could spark an unintended rise in interest rates, according to minutes of their July meeting released Tuesday.

The Policy Board voted at the meeting to keep its benchmark for 10-year government bond yields at around zero percent while saying that yields "may move upward and downward to some extent."

One member warned that "making policy adjustments that could allow the long-term yields to rise might lead to an increase in real interest rates," making it more difficult to lift inflation toward the central bank's 2 percent target, the minutes showed.