Global central banks, including the Bank of Japan, buying assets and keeping interest rates low to boost growth have had "positive short-term effects for banks" even as risks from the policies are increasing, the International Monetary Fund said.

"The prolonged period of low interest rates and central bank asset purchases has improved some indicators of bank soundness," the IMF said Thursday in its Global Financial Stability Report. "Central bank intervention mitigated dysfunction in targeted markets, and large-scale purchases of government bonds have in general not harmed market liquidity."

Central banks in the U.S., Europe, Japan and the U.K. attacked the longest and deepest recession since the 1930s with unorthodox accommodation.