Japanese Finance Minister Taro Aso said on Friday that he would firmly respond to currency market movements if necessary to prevent "extremely nervous moves" from continuing, while closely watching movements with a sense of urgency.
Aso declined to comment when asked about the possibility of coordinated intervention in the currency markets and whether Japan had intervened to stem the yen's strength, after media reports said Britain had voted to leave the European Union.
Japan's policymakers are worried a Brexit vote could boost demand for the safe-haven yen and trigger an unwelcome rise in the Japanese currency that would hurt Japan's exports.