Overseas fund purchases of Japanese government bonds reached the second-highest level on record in June as the spread of the Delta mutation spurred investor demand for safe-haven assets.

Overseas investors bought a net 4.06 trillion yen ($37 billion) of JGBs last month, second only to 4.42 trillion yen in December 2018, according to the Japan Securities Association.

Sumitomo MitsuiKei Yamazaki, senior fund manager at DS Asset Management, said: "although JGBs are not attractive in themselves, their inclusion in the global fund index may benefit from the acceleration of global bond purchases. Profit-taking in the stock market may also lead money into the bond market. "

Bond yields around the world are falling amid fears that an outbreak caused by the Delta virus could slow the global economic recovery. The yield on the 10-year US Treasury note fell below 1.50 per cent in June, while the yield on Japanese government bonds also fell and is now close to zero.