The yen jumped briefly against the dollar on Friday, putting traders on alert for signs of fresh intervention by Japanese authorities, who likely stepped in the previous day to prop up a currency still close to its lowest in 38 years.

The dollar fell as much as 1% to a one-month low of 157.30 yen, but pared some of those losses to trade down 0.55% at 158.01 yen. The euro was last down 0.2% at 172.28 yen.

Japan's top currency diplomat Masato Kanda declined to say whether forex market intervention or a rate check were conducted, Jiji Press reported on Friday. He did say that the fact that there had been a one-sided, speculative move in exchange-rate fluctuations could not be ignored.

Japan's Ministry of Finance and the New York Federal Reserve were not immediately available for comment sought by Reuters.

Daily operations data earlier in the day suggested the Bank of Japan (BOJ) may have spent over 3 trillion yen ($18.85 billion) on defending the currency on Thursday, less than three months after it last intervened.

It was not immediately clear what was behind this latest move. Several analysts noted that it bore some of the hallmarks of official buying, but the yen's strengthening was more modest than Thursday's, raising some doubt as to whether or not the central bank was behind the trend.

"It could be a modest further round of intervention. I wouldn't be as confident as yesterday when the move was much bigger," said Chris Scicluna, head of economic research at Daiwa Capital Markets.