State giants Vietcombank and BIDV sold the greenback at VND23,840, up 0.04% from Wednesday.
The State Bank of Vietnam (SBV) fixed its reference rate at VND23,316, up 0.64% from Wednesday and up 0.7% since the beginning of the year.
The USD Index, which measures the dollar against six major currencies, rose by 1.1% to 111.26 points Thursday morning, a 20-year high after the U.S. Federal Reserve increased its policy rates by 0.75% points for a third time in a row to control inflation.
The SBV has sold more than $20 billion from its reserves this year to steady the exchange rate, according to ACBS Securities, which said the reserves have fallen from $110 billion to below $90 billion.