TOKYO, April 21 (Reuters) - Japanese government bond yields fell on Wednesday, as investor appetite for safe-haven debt was boosted by a drop in stocks on fears that possible COVID-19 lockdowns in Japan’s biggest cities would delay an economic reopening. The 10-year JGB yield fell 1.5 basis points to 0.065%, while the 20-year JGB yield fell 1.5 basis points to 0.425%. The 30-year JGB yield declined two basis points to 0.620%. The two-year JGB yield fell 0.5 basis point to minus 0.135% and the five-year yield declined 0.5 basis point to minus 0.105%. The 40-year JGB yield fell one basis point to 0.665%. Benchmark 10-year JGB futures rose 0.19 point to 151.57, with a trading volume of 26,802 lots. The Nikkei share average tumbled nearly 2%, after losing the most in about a month a day earlier. (Reporting by Tokyo markets team; Editing by Subhranshu Sahu)