TOKYO, June 21 (Reuters) - The yield on 10-year Japanese government bonds (JGBs) tracked declines on U.S. Treasury yields on Monday, while sharp sell-offs in Japanese equities boosted safe-haven demand for fixed income. The 10-year JGB yield fell 1.5 basis points to 0.040%, while the 20-year JGB yield fell 0.5 basis points to 0.425%. The 30-year JGB yield was unchanged at 0.670%, while the 40-year JGB yield rose 0.5 basis points to 0.740%. The two-year JGB yield rose 0.5 basis points to minus 0.120%. The five-year yield was flat at minus 0.105%. Benchmark 10-year JGB futures rose 0.18 points to 151.8, with a trading volume of 21,712 lots. The U.S. 10-year Treasury yield fell to its lowest since March during Asian trading hours. (Reporting by Tokyo markets team; Editing by Jan Harvey) Our Standards: The Thomson Reuters Trust Principles.