The yield on Japan's benchmark 10-year government bonds hit a new low of minus 0.165% on Monday. 
Investors are buying Japanese government bonds, which are considered relatively safe, on concerns over Britain's referendum on whether or not to leave the European Union, according to Japan's (NHK WORLD) radio. 
Analysts say investors are also buying government bonds in Germany and other countries to avert risk, ahead of the June 23rd referendum.