Japan's efforts to check its rising currency against the U.S. dollar included an as-yet-unannounced sale of 1.02 trillion yen in November, data showed Tuesday.
The early November currency market intervention to stem the rising value of the yen was worth $13.3 billion, Finance Ministry data showed, Kyodo News reported.
Such a yen sale, referred to as "masked intervention'' by Japanese market participants and "stealth intervention" by others, came on the heels of a record 8.07 trillion yen ($105.2 billion) intervention on Oct. 31 after the yen jumped to a post-World War II high of 75.32 against the greenback.
The October intervention was promptly announced by the Finance Ministry and Japan's central bank, Kyodo said.
Japan, whose economy is largely driven by exports, needs to keep its yen from appreciating too much as that would make its goods more expensive against other currencies, hurting exports.
However, some experts say such open interventions have not been effective as the yen has continued to rise.
The Wall Street Journal reported the Japanese Finance Ministry covertly purchased dollars with its yen between Nov. 1 and Nov. 4 through its "stealth" intervention.
The Journal quoted an official source as saying, "We made a judgment that (stealth intervention) was the most effective way" to check the yen's rise. The dollar moved up after that.
The journal said the Oct. 31 intervention pushed the dollar to 79.55 yen and by the end of Nov. 4 it was at around 78.22 yen.
The Journal reported the government source declined to comment on whether U.S. financial authorities were informed prior to the stealth intervention. However, the U.S. Treasury said in its late December report that it did not back the earlier interventions.