The yield on the benchmark 10-year Japanese government bond briefly rose to a level not seen in about seven-and-a-half years.
It hit 0.54 percent on Friday morning.
Market sources say many investors are selling JGBs on speculation the Bank of Japan may again taper its relatively loose policy.
The BOJ decided in its December meeting to allow the yield on the 10-year bonds to move in a range of plus or minus 0.5 percent.
The earlier range was plus or minus 0.25 percent.
The rising JGB yield fueled speculation that Japan's interest rates could move closer to those in the United States.
The Japanese currency rose against the US dollar as a result, climbing to the upper 128-yen level at one point on Friday.