The Bank of Japan cut its key interest rate effectively to zero Tuesday, pledging to hold that line until the end of deflation is in sight.

Adding to the surprise news, the BOJ also said it will set up a ¥5 trillion fund to buy various financial assets, ranging from long- and short-term government securities, commercial paper, corporate bonds, exchange-traded funds and Japan real estate investment trusts, in an effort to lower long-term interest rates as well as to encourage investors to buy financial products with risks.

The BOJ's actions were credited with sparking a Tokyo stock surge and minor rise in the dollar.