The 10-year yield, which had been stuck around 0.25% for months because of the central bank cap, quickly moved up to 0.46% in afternoon trading. 

The yen rose in tandem. In Tuesday afternoon trading in Tokyo, one dollar bought between 133 and 134 yen, compared with more than 137 yen before the BOJ’s decision.

The Nikkei Stock Average, which had been slightly higher in the morning, was down more than 2% as investors digested the possibility that companies would have to pay higher interest on their debt. Also, the weak yen has pushed up profits for many exporters, so a stronger yen could be negative for stocks. 

Gov.

Haruhiko Kuroda,

who is nearing the end of 10 years in office, is known for making moves that surprise the market, although he had made fewer of them in recent years.

Market players had anticipated that time might be running out on the Bank of Japan’s low-rate policy, but they generally didn’t expect Mr. Kuroda to move at the year’s final policy meeting.

The Bank of Japan’s statement on its decision Tuesday didn’t mention inflation as a reason to let the yield on government bonds rise as high as 0.5%. Instead, it cited the deteriorating functioning of the government bond market and discrepancies between the 10-year government bond yield and the yield on bonds with other maturities. 

The bank said Tuesday’s move would “facilitate the transmission of monetary-easing effects,” suggesting it didn’t want the decision to be interpreted as monetary tightening.

The move is “a small step toward an exit” from monetary easing, said

Mitsubishi UFJ Morgan Stanley Securities

strategist Naomi Muguruma. 

Ms. Muguruma said the BOJ needed to narrow the gap between its cap on the 10-year yield and where the yield would stand if market forces were given full rein. 

“Otherwise magma for higher yields could build up, causing the yield to rise sharply when the BOJ actually unwinds easing,” she said. 

Japan’s interest rates are still low compared with the U.S. and Europe, largely because its inflation rate hasn’t risen as fast. The Federal Reserve last week raised its benchmark federal-funds rate to a range between 4.25% and 4.5%—a 15-year high—while the European Central Bank said it would raise its key rate to 2% from 1.5%.

In the U.S., inflation has started to slow down recently but is still running above 7%. In Japan, consumer prices in October were 3.7% higher than they were a year earlier.

Japan has seen prices rise like other countries, owing to the impact of the war in Ukraine as well as the yen’s weakness. However, the pace of inflation is milder in Japan, where consumers tend to be highly price sensitive.

Write to Megumi Fujikawa at megumi.fujikawa@wsj.com