TOKYO, May 6 (Reuters) - Yields on benchmark 10-year Japanese government bonds fell on Thursday, tracking overnight U.S. Treasury yields lower, after investors marked moderately successful results of the Bank of Japan’s bond-buying operation. *The 10-year JGB yield fell 0.5 basis point to 0.085%. *The 20-year JGB yield fell 0.5 basis point to 0.450%. *The two-year JGB yield was unchanged at minus 0.130%. *The five-year yield fell 0.5 basis point to minus 0.100%. *The 40-year JGB yield rose 0.5 basis point to 0.705%. *Benchmark 10-year JGB futures rose 0.07 point to 151.41, with a trading volume of 14,926 lots. (Reporting by Tokyo markets team, Editing by Sherry Jacob-Phillips) Our Standards: The Thomson Reuters Trust Principles.