TOKYO, June 9 (Reuters) - Japanese government bond yields fell on Wednesday, led by the longest-dated securities, as bonds continued to be bought following Tuesday’s smooth 30-year debt auction and declines in U.S. Treasury yields overnight. The 30-year JGB yield fell 1.5 basis points to 0.665%, with the 20-year yield also declining 1.5 basis points to 0.430%. “Yesterday’s 30-year auction was on the strong side compared to what the market had been expecting, and that came as a relief to investors so they continue to buy back bonds today,” said Takenobu Nakashima, chief rates strategist at Nomura Securities. The 40-year JGB yield fell 1 basis point to 0.710%. The 10-year JGB yield fell 0.5 basis point to 0.065%, while benchmark 10-year JGB futures rose 0.09 point to 151.71, with a trading volume of 41,156 lots. The five-year yield was flat at minus 0.105%, and two-year JGBs were untraded. (Reporting by Tokyo markets team; Editing by Rashmi Aich) Our Standards: The Thomson Reuters Trust Principles.