Finance Minister Shunichi Suzuki cautioned against the recent and rapid decline of the yen on Monday.

"We will respond appropriately if there are excessive moves (on the foreign exchange market)," Suzuki told reporters, issuing a warning against speculative trading. "We will keep a close watch (on the market) with a strong sense of caution."

That same day, Masato Kanda, Japan's top currency diplomat, told reporters separately that the current exchange market moves are "rapid and one-sided," adding, "We will monitor the situation with a high sense of urgency and take appropriate responses to excessive moves."