Bank of Japan Deputy Governor Masayoshi Amamiya said that the central bank must "patiently continue" its powerful monetary stimulus to maintain momentum towards achieving 2% inflation, as downside risks from overseas economies mount.

"The BOJ will appropriately guide policy without preconception, while monitoring various risks," Amamiya said in a speech at an annual meeting of credit associations.

More attention is needed than before to risks that price momentum will be lost, Amamiya said. With that in mind, the central bank will re-examine the economy and price trends at its policy-setting meeting scheduled for Oct. 30-31, he said.