SINGAPORE—The yen firmed on Thursday, returning towards a four-month peak against the dollar hit earlier in the week after the Bank of Japan’s surprise tweak to its bond yield control spurred bullish yen bets, while the dollar moved broadly lower. The yen rose about 0.5 percent to 131.85 per dollar, after surging to a four-month…

SINGAPORE/LONDON—The yen traded flat on Wednesday after surging almost 4 percent in the previous session, when the Bank of Japan (BOJ) unexpectedly tweaked a key policy, allowing government bond yields more room to move. The BOJ decided to change its “yield curve control” policy on Tuesday even as it kept broad policy settings unchanged. It…

LONDON—The yen surged to a four-month peak against the dollar on Tuesday after the Bank of Japan stunned markets by deciding to review its yield curve control policy and widen the trading band for the 10-year government bond yield. While it kept broad policy settings unchanged—pinning short-term JGB yields at -0.1 percent and the 10-year…