The Bank of Japan on Friday eased monetary policy by boosting the size of its asset purchase program by ¥5 trillion, saying the move will "better ensure the return of Japan's economy to a sustainable growth path with price stability."

The decision raises the size to ¥70 trillion, which will be used to purchase financial instruments, including Japanese government bonds.

The bank's second easing in three months is an effort to support economic activity by encouraging a decline in longer-term interest rates and risk premiums, and by bolstering market stability, the BOJ said in a statement following the two-day Policy Board meeting.