The Bank of Japan last week decided to allow the yield on the 10-year government bond to move in a wider range.

The yield had already been inching upward. Now, banks and other lenders are responding with rate hikes of their own. That means higher costs for borrowers, including people with mortgages.

Resona Bank has raised its prime interest rate on 10 year fixed-rate housing loans by 0.05 percentage point. It's been 0.75 percent since Wednesday.

Mizuho Bank and Sumitomo Mitsui Trust Bank hiked the interest rates on their 15-year and 20-year fixed-rate loans by 0.05 percentage point.

Analysts expect mortgage costs to continue rising as long as that government-bond yield continues creeping up.