The Bank of Japan maintained its zero interest rate policy Wednesday while offering a somber assessment of global financial markets, saying close attention is needed "mainly due to concern about the European debt problem."

"There remains a high degree of uncertainty about the global economy, including the prospects for the European debt problem" and the momentum toward recovery in the U.S. economy, the central bank said in a statement following a two-day meeting of its Policy Board.

"Careful attention should be paid to future developments in international commodity prices and in medium- to long-term inflation expectations," the BOJ said.