Emerging Asian currencies also found support from strong stock markets and a broadly weak dollar, with the Malaysian ringgit hitting a 14-year high and the Indonesian rupiah touching a seven-year high.
Apart from South Korea, other regional foreign exchange authorities also have been spotted buying dollars in recent sessions to check gains in their currencies, but the moves are unlikely to halt their bullish trend, analysts and dealers said.
Asian central banks also buy the euro with dollars from intervention, helping to buoy the European single currency, which will eventually support Asian currencies.
"Intervention can slow things down, but cannot reverse the strengthening trend," said Frances Cheung, a strategist at Credit Agricole CIB in Hong Kong.
Emerging Asian currencies have been supported by inflows into regional stocks and bonds on stronger economic growth as well as expectations that policymakers are making efforts to contain inflation.
"Asian currencies have further room to go as more money is going to countries with more sound fiscal balance and better fundamentals. Moreover, emerging Asian currencies will be more attractive as policymakers will allow more appreciation," said Shin Dong-jun, a fixed-income analyst at Dongbu Securities in Seoul.
WON
Hedge funds boosted the won to a fresh 32-month high against the dollar, despite dollar buying by authorities and news that the government may reduce ceilings on bank's currency derivatives as early as next month, a move widely seen as aimed at taming the currency's rally.
Authorities said in a joint statement that banks' forex derivatives positions would be inspected from next week.
The moves kept the South Korean currency weaker than 1,080 per dollar, but it still ended 0.3 percent higher on the day.
The currency strengthened to as firm as 1,078.3, the strongest since Aug. 2008, in the afternoon as investors took advantage of the intervention and bought it on the dip.
"The momentum was so strong that investors can ignore the plan. For now, people are interested only in how strong intervention would be," said an Asian bank dealer in Singapore.
Another dealer said the government would allow more appreciation as it is focusing on fighting inflation.
"I think it (the inspection plan) is in line with already outstanding policy guidance that is aimed at slowing won gains, rather than halting them," Said Sacha Tihanyi, a senior currency strategist at Scotia Capital in Hong Kong.
"As such, I'd still be bullish KRW at least until the end of the month. I don't think that this will stop (on its own) the won's ability to strengthen."
The $2 billion intervention was believed to be the strongest daily dollar-buying by authorities so far this year, traders said.
Foreign investors posted their biggest daily stock purchases since July 2010 and local interbank speculators reduced dollar holdings amid weakness in the greenback.
SINGAPORE DOLLAR, RUPIAH
The Singapore dollar hit a fresh record high and the Indonesian rupiah touched a seven-year peak on little sign of intervention by their central banks.
The Singapore dollar strengthened to as firm as 1.2346 versus the greenback.
"At the moment, it is just tracking the USD weakness with EUR, AUD and CNY all higher... So, basket wise, it is within limits, I reckon," said a European bank dealer in Singapore.
The Monetary Authority of Singapore was spotted in previous session at around 1.2390-1.2400, but pulled out bids when the US dollar stayed weak, he added.
The rupiah rose to 8,610 per dollar, the strongest since April 2004, on inflows to Indonesian stocks and bonds.
"We are hearing BI checking for levels earlier. But with USD/Asian going lower altogether, BI will allow some room to fall," a European bank dealer in Jakarta said.
RINGGIT
The ringgit hit a fresh 14-year high against the dollar on interbank speculators' demand.
The Malaysian currency strengthened to as firm as 3.0040, the strongest since Sept. 1997.
The central bank was spotted buying dollars at 3.0120 initially, but lowered its bids gradually, dealers said.
TAIWAN DOLLAR
The Taiwan dollar rose to its highest in more than two months on foreign buying and a rally in local stocks.
Foreign investors made their biggest daily purchase of stocks in more than two weeks.
The island's currency strengthened to as firm as 28.870, the strongest since Feb. 10.
However, the gain was capped in part by the central bank, said dealers.