The yen also briefly rallied against the euro , sterling and Australian dollar before paring those gains. The euro was last up 0.7% against the yen, while the pound and the Aussie were up between 0.6% and 1%.

The Japanese yen slid on Friday, having briefly jumped against the dollar and other currencies, leaving traders on high alert for signs of buying by Japan's monetary authorities after the central bank left interest rates on hold at its latest meeting.

The dollar suddenly fell sharply to 155 yen from 156.8, before tracking back to around 156.44, still up 0.5% on the day. It was not immediately clear what caused the move and the yen remained near 34-year lows struck earlier in the day.

The yen also briefly rallied against the euro , sterling and Australian dollar before paring those gains. The euro was last up 0.7% against the yen, while the pound and the Aussie were up between 0.6% and 1%.

Japan's Ministry of Finance was not immediately available for comment.

"The MOF is almost duty-bound to go in and send a message to markets and the trading community is bound to challenge that," Kit Juckes, currency strategist at Societe Generale, said.

"What bothers me is that dollar/yen is not going up in a disorderly way for the MOF to whack it back down the other way."

One London-based currency analyst said he suspected the move in dollar/yen was down to a position squeeze that sparked others to sell dollar/yen in a nervous market.

Traders have been on watch for weeks for possible intervention by Japanese officials, as even a historic exit from negative rates has failed to lift the currency.

Bank of Japan governor Kazuo Ueda told a press conference after the rate decision earlier in the day that monetary policy does not directly target currency rates, although exchange-rate volatility could have a significant impact on the economy and prices.

As to whether those effects are good or bad he said: "The weak yen has an impact on demand, including some positive effects. This, in turn, will determine underlying inflation in the medium- to long-term."

Japan intervened in the currency market three times in 2022, selling the dollar to buy yen, first in September and again in October as the yen slid towards a 32-year low of 152 to the dollar.

The yen has been under pressure for years as U.S. interest rates have climbed and Japan's have stayed near zero, driving cash out of yen and into dollars to earn so-called "carry".