HANOI, May 2 (Xinhua) -- Vietnam's central bank on Wednesday increased its reference exchange rate between Vietnamese dong and U.S. dollar by 9 Vietnamese dong to 22,548 Vietnamese dong per U.S. dollar.

With the current trade band of plus or minus 3 percent, the ceiling exchange rate is 23,241 Vietnamese dong per U.S. dollar, and the floor rate is 21,797 Vietnamese dong per U.S. dollar, said the State Bank of Vietnam.

Meanwhile, listed rates at big commercial banks in Vietnam fluctuated marginally. Vietcombank raised both rates by 5 Vietnamese dong, buying the greenback at 22,735 Vietnamese dong per U.S. dollar and selling at 22,805 Vietnamese dong per U.S. dollar.

BIDV and Vietinbank lowered their rates by 5 Vietnamese dong and 6 Vietnamese dong, respectively.

The reference exchange rates saw four ups last week with total magnitude of 41 Vietnamese dong per U.S. dollar.

According to Vietnam's National Financial Supervisory Commission, the central exchange rate in late 2017 rose around 1.6 percent against early 2017, while the average rate offered by commercial banks decreased 0.2 percent, and on the free market dropped some 1.5 percent.