The Japanese yen surged more than 2% against the US dollar on Thursday, reaching its strongest level in a month at 155.57, after a Bank of Japan policymaker signalled the central bank may move more decisively on borrowing costs. Board member Hajime Takata's call to act more "nimbly" on rates raised market expectations of an imminent hike, with investors now pricing in a 77% probability of a rate rise at the BoJ's next policy meeting beginning 17 September. The move adds to turbulence in global financial markets already rattled by a bond sell-off driven by inflation fears, while Japan's vice-finance minister warned that officials remain on "heightened alert" over currency and market conditions.