The dovish tone in the Fed's policy statement helped boost risk sentiment across Asia on Thursday helping the regional currencies too strengthen against a broadly weak greenback.
The Singapore dollar and Thai baht hit new multi-month highs while their peers in Indonesia, China and Malaysia also gained sharply on the day.
At 11:30 am in Singapore, the STI index was up 1.2%. Hong Kong's Hang Seng and Japan's Nikkei 225 were up more than 1.3% and South Korea's KS11 was up 1.1%. Indonesia's JKSE and Malaysia's KLSE were up more than 0.6% as Taiwan's TWII rose nearly 0.5%.
The Singapore dollar traded at 1.3611/US dollar, its strongest since late July last year, and compared to the previous close of 1.3648. USD/THB fell to 34.80, making the baht's strongest in 8 months and from Wednesday's close of 34.88.
The Malaysian ringgit strengthened to 4.0663/US dollar, very close to the 11 march 7-month high of 4.0645 and from the previous close of 4.1515.
USD/IDR slipped t0 13,138 from Wednesday's close of 13,270, heading back near the 10-month high of 13,000 touched on Monday.
Analysts said the concerns raised by the US central bank regarding the health of the recovery of world's largest economy indicated that foreign investments to emerging Asian markets will continue with more ease.
It was in line with expectations that the Fed leaving rates on hold but the market players got an extra pinch of dovish tone in the Chair's statement.
"I am wary and have not yet concluded that we have seen a significant uptick that will be lasting," Fed Chairperson Janet Yellen said at the press conference following the two-day policy meeting that concluded on Wednesday.
"Removing interest rate risk from the near horizon has been enough to coax money back into risky assets, but price increases in gold and the depreciation of the dollar would indicate that quantification of the degree of risk still varies greatly," according to Martin King, co-managing director at Tyton Capital Advisors, a Reuters article said.
