The LDP's victory will propel ex-Prime Minister Shinzo Abe - who has called for "unlimited" monetary easing, an increase in the inflation target and big spending on public works to rescue the economy - back to power.
Analysts expect the prospect of ultra-loose monetary policy to weaken the yen further in coming weeks, depending on the pace of policy change. However, given that bets against the yen are already hefty, losses could be limited.
The dollar was last up 0.3 percent on the day at 83.70 yen , having earlier hit 84.48 yen, its strongest since April 2011.
This left it with the potential to target the 200-week moving average at 85.008 yen.
The LDP's huge victory will give the new government a greater chance of pushing through policies.
The LDP and its ally the New Komeito party secured the two-thirds majority needed to overrule parliament's upper house.
"The fact that the LDP secured a two-thirds majority gives them a strong mandate and will lead to significant policy changes," said Ian Stannard, head of European currency strategy at Morgan Stanley.
"The yen weakening trend will be sustainable and dollar/yen will move higher while euro/yen also has the potential to move sharply higher." He said Morgan Stanley forecasts the dollar to rise to 90-92 yen by the end of 2013, while the euro could rise to 113 yen by the end of this year.
The euro jumped to around 111.30 yen, its highest since late March.
It eased back as some funds liquidated long euro position, leaving it last up 0.2 percent at 110.15 yen.
The next test is this year's high of 111.43 yen, with support said to lie at Friday's session high of 109.98 yen.
The Bank of Japan is scheduled to meet on Wednesday and Thursday.
The BoJ will most likely increase its asset-buying and lending programme, currently at 91 trillion yen, by another 5-10 trillion yen, sources have said.
The euro's gains against the yen also helped it against the dollar.
It was last steady at $1.3155, having hit $1.3192 in Asia, its highest in eight-and-a-half months.
Analysts said the dollar may be hampered by any signs of troubles in US talks to avert a "fiscal cliff" of $600 billion worth of tax increases and spending cuts due next month.
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