RIO DE JANEIRO (Reuters) -Japan has warned of the need to be increasingly vigilant to excessive foreign exchange fluctuations driven by speculation at a Group of 20 meeting, top currency diplomat Masato Kanda said on Thursday.

"Japan has said we must respond appropriately based on G20 comittments that excessive currency volatility has a negative impact on the economy and financial stability," Kanda said.

He made the comments during a press conference at the G20 finance ministers and central bank governors meeting in Rio de Janeiro, Brazil.

The Japanese yen rallied for a fourth session against the dollar on Thursday, hitting the highest in more than two months, as investors unwound their long-running bets against the currency ahead of a Bank of Japan meeting next week.