The Bank of Japan announced an unscheduled bond-purchase operation on Wednesday in an effort to curb the pace of gains in sovereign yields after it tweaked policy on Tuesday.

The operation had little immediate impact on the benchmark 10-year bond yield. It touched a fresh decade-high of 0.97% on Wednesday.

Bond futures pared their losses slightly after the announcement, while the 10-year yield was little changed at 0.96%. The yen pared its gains slightly versus the dollar.

The Japanese 10-year yield was just 0.44% on July 27, one day before the central bank’s first tweak to yield-curve control this year to make it more flexible. The BOJ has also resorted to increasing purchase amounts in regular operations to rein in the yield advance.

--With assistance from Naoto Hosoda.