Former Bank of Japan Gov. Masaaki Shirakawa stressed the need to take unconventional steps to help underpin the economy in October 2010 but cautioned that the decision to purchase exchange-traded funds would entail risks, meeting minutes showed Monday.

The BOJ decided on its first-ever purchase of ETFs, which are riskier in terms of price volatility than assets the bank had previously bought, at a policy meeting on Oct. 5 of the year under what it called "comprehensive monetary easing."

"It means that we cannot make up for possible losses with (money in) our pocket, but would pass the burden on to the public," Shirakawa said in warning other BOJ policy members of the risk if stock prices fell and other assets it bought lost value, according to the minutes.