The Bank of Japan decided to keep its current monetary policy unchanged Thursday, and upgraded the assessment of the economy.

The BOJ's Policy Board voted unanimously to maintain its key short-term interest rate at around zero to 0.1 percent and decided to maintain its plan to expand the size of its asset purchase program to 101 trillion yen (1.08 trillion US dollars) by the end of this year.

The BOJ also upgraded its assessment of Japan's economy from " relatively weak" up to "appears to have stopped weakening."