The Bank of Japan kept its ultraloose monetary policy unchanged Tuesday while upgrading its assessment of the domestic economy, citing signs of recovery in exports and investment.

"Last month we mentioned that the economy is starting to pick up, but we have changed our (assessment) to describe the economy as 'picking up,' " BOJ Gov. Haruhiko Kuroda told reporters after the central bank's two-day Policy Board meeting.

On the recent volatility of the Nikkei 225 stock average and long-term interest rates for Japanese government bonds, Kuroda was unfazed, saying the situation "will eventually regain stability."