Any respite from such an intervention appeared to be brief, however, with dollar/yen rising 1.3% to 149.54 in early trade on Monday before easing slightly on fears of more interventions.
Sources told Reuters that the dollar's plunge by as much as by 7 yen overnight on Friday was caused by authorities' yen-buying action for the second time in as many months. On Sept. 22 they stepped in to prop up the yen for the first time since 1998.
Japan announced that intervention but has since remained mum on whether it were taking any further action in the currency market.
"I won't comment," Finance Minister Shunichi Suzuki told reporters at the finance ministry, when asked about intervention.
"We absolutely cannot tolerate excessive moves in the foreign exchange market based on speculation," Suzuki told reporters at the finance ministry.
Masato Kanda, vice finance minister for international affairs, also declined to comment on intervention.
Both Suzuki and Kanda said they were ready to take appropriate steps against any excessive currency volatility.