The yen hit its lowest level in nearly four years against the dollar in Asian trade on Monday following the Bank of Japan's sweeping stimulus last week.
The dollar bought 98.56 yen in Tokyo, up from 97.54 yen in New York late Friday, hitting its highest level since June 2009 and boosting Japanese exporter shares.
"Financial 'shock and awe' may not be too inappropriate a description" of the easing steps announced by the Bank of Japan (BoJ) last week, National Australia Bank said.
"Having comfortably leapfrogged market expectations for what the new BoJ regime... was likely to deliver at its first outing, the explosive Japanese yen reaction was justified and should have further to run," it said.
"We expect 100 yen to be surpassed sooner rather than later," it said in a note.
The euro also rose to 127.96 yen from 126.70 yen in US trade while buying $1.2994 against $1.2990.
The euro-yen is likely to trade in a 127.00-129.00 range Monday, said a senior dealer at a major bank in Tokyo, noting investors would likely take cues from the dollar-yen moves.
"But market volatilities have just been too high, and I'm getting irritated at that," he told Dow Jones Newswires.
BoJ governor Haruhiko Kuroda surprised markets Thursday by announcing bolder-than-expected easing steps.
Kuroda said the bank would boost money supply massively and jack up asset purchases to hit a two-percent inflation target, vowing no let-up in the battle against falling prices that have plagued the economy for decades.
Capital Economics said a further significant fall in the yen probably lay ahead, predicting the dollar-yen rate at 105 at the end of 2013 and 120 at end-2014.
The Australian dollar fell to $1.0369 from $1.0418 on Friday while the Chinese yuan rose to 15.86 yen from 15.53 yen.
Australian Prime Minister Julia Gillard said Monday that Canberra and Beijing had reached an agreement to allow each other's currencies to be directly converted in a move to slash costs for companies doing business in China.
It will be possible from Wednesday to directly convert yuan into Australian dollars, and vice versa, making Australia only the third country to have such a currency arrangement in place with Shanghai after the United States and Japan.
"This is a huge advantage for Australia," Gillard told reporters in Shanghai. "It's a strategic step forward for Australia as we add to our economic engagement with China."
The dollar was also higher against most other Asia-Pacific currencies Monday.
It rose to 1,138.85 South Korean won from 1,129.03 won, to 41.30 Philippine pesos from 41.19 pesos, to Sg$1.2411 from Sg$1.2397, to Tw$30.00 from Tw$29.92, and to 9,761 Indonesian rupiah from 9,756 rupiah.
But it eased to 54.69 Indian rupees from 54.79 rupees and to 29.32 Thai baht from 29.35 baht.