After the dollar rose to 151.94 yen , its highest since 1990, the intervention drove the Japanese currency down more than 7 yen to a low of 144.50 yen.
Register now for FREE unlimited access to Reuters.com RegisterThe Ministry of Finance (MOF) intervened in several stages from around 9:35 p.m. (1235 GMT), one source said.
Speaking to reporters shortly after the yen spiked, Japan's top currency diplomat, Masato Kanda, declined to comment on whether the MOF had intervened, according to Jiji news agency.
Many market players doubt whether Tokyo can reverse the yen's downtrend with solo intervention, even with Japan's $1.33 trillion in foreign reserves.
Japan bought a record 3.6 trillion yen ($24 billion) in the September action, Tokyo money market brokerage firms estimated.