Bank of Japan Governor Toshihiko Fukui said on Friday the central bank needs to keep a close eye on recent rises in long-term rates and how they could affect Japan's economic and price outlook.
"The recent movements in long-term rates are a relatively new phenomenon so we need to watch them closely," Fukui told a news conference after the BOJ's policy board, as expected, voted unanimously to keep interest rates on hold.
Fukui said it would be "very problematic" if the rise in bond yields signalled that market players are cautious about rising inflationary expectations.
But he added that inflationary expectations remain stable globally for now.
Japanese bond yields have risen sharply since late last month on surging yields of U.S. Treasuries and on expectations that a recent batch of upbeat economic data would lead to an early BOJ rate hike.
The BOJ has stood pat on policy after raising its key policy rate to a decade-high 0.5 percent in February, which was the first rate rise since July last year.