Citing calculations made by Tokyo money market brokerage firms, Reuters reported on Monday that Japan's intervention in the foreign exchange market on September 22 is estimated to be around 3.6 trillion yen ($25 billion).
Japan's Ministry of Finance is expected to unveil the actual amount spent during the intervention on Friday.
"The uncertainty over Japan's economy is extremely high, we must keep the ultra-easy policy to support the economy," Bank of Japan (BoJ) Governor Harihuko Kuroda said earlier in the day.
Market reaction
USD/JPY largely ignored this headline and was last seen trading at 143.80, where it was up 0.35% on a daily basis.