TOKYO, May 21 (Reuters) - The price of 20-year Japanese government bonds firmed on Monday as some traders bought the maturities in expectations of healthy demand at an auction the following day.
The move came after data from brokerage industry group Japan Securities Dealers Association showed big Japanese banks sold 1.356 trillion yen ($12.18 billion) of super-long bonds in April, their first net selling in the sector.
Traders expected these banks to rebuild their positions at Tuesday's auction of 1.0 trillion yen ($8.98 billion) 20-year JGBs. The optimistic mood also stemmed in part from strong results of a 30-year JGBs auction held last Tuesday.
The 20-year JGB yield fell 0.5 basis point to 0.535 percent, while the 30-year JGB yield fell 0.5 basis point to 0.755 percent.
The 10-year JGB yield was flat at 0.055 percent while 10-year JGB futures ended up 0.01 point at 150.71, with a trading volume of 21,768 lots. ($1 = 111.36 yen) (Reporting by Tokyo Markets Team; Editing by Sunil Nair)