Japan ramped up its warnings against currency speculation Friday after the yen slid to a five-month low following a hint from the central bank chief that he may wait longer than expected before raising interest rates.

"The government is deeply concerned about recent currency moves, including those driven by speculators,” Finance Minister Katsunobu Kato said on Friday. "We will take appropriate action if there are excessive moves in the currency market.”

The yen regained some ground against the dollar after Kato’s remarks, strengthening to as much as ¥156.89 after earlier weakening to as much as ¥157.93. The Japanese currency strengthened a little further after currency chief Atsushi Mimura also backed up Kato with similar comments in the afternoon.