TOKYO, Aug 23 (Reuters) - Benchmark Japanese government bonds were steady on Wednesday, while the prices of longer maturities edged down from their gains in the previous session following a solid 20-year auction.
The 10-year cash JGB yield was flat at 0.035 percent, while the September 10-year JGB futures contract finished up 0.03 point at 150.77.
But the 20-year JGB yield added one basis point to 0.550 percent, while the 30-year JGB yield was up half a basis point at 0.835 percent.
On Tuesday, the bid-to-cover ratio at the Ministry of Finance's 20-year sale rose to 4.51 from the previous auction's 4.19, suggesting stronger demand for the bonds.
In its regular JGB purchase operations on Wednesday, the Bank of Japan offered to buy JGBs in the same volume as previous offers, which included 280 billion yen ($2.56 billion) of one-year to three-year JGBs, 330 billion yen of three-year to five-year JGBs and 200 billion yen of 10-year to 25-year JGBs.
($1 = 109.4600 yen) (Reporting by Tokyo markets team; Editing by Eric Meijer)