TOKYO, April 26 (Reuters) - Japanese government bond (JGB) yields rose on Monday as somewhat weak results of the Bank of Japan’s bond buying operation weighed on investor sentiment. *The 10-year JGB yield rose 0.5 basis point to 0.070%. *The 20-year JGB yield rose 0.5 basis point to 0.435%. *The 30-year JGB yield rose one basis point to 0.645%. *The five-year yield rose 0.5 basis point to minus 0.105%. *Benchmark 10-year JGB futures fell 0.08 point to 151.48, with a trading volume of 16,168 lots. (Reporting by Tokyo markets team)