HANOI, Sept. 28 (Xinhua) -- Vietnam's central bank on Friday adjusted its reference exchange rate between Vietnamese dong and U.S. dollar down by 1 Vietnamese dong to 22,714 Vietnamese dong per U.S. dollar.

With the current trading band of plus or minus 3 percent, the ceiling exchange rate is 23,395 Vietnamese dong per U.S. dollar, and the floor rate is 22,033 Vietnamese dong per U.S. dollar, said the State Bank of Vietnam.

Meanwhile, listed rates at big commercial banks in Vietnam remained unchanged or dropped slightly from Thursday. Vietcombank kept both rates at 23,310 Vietnamese dong per U.S. dollar for buying and 23,390 Vietnamese dong per U.S. dollar for selling.

Rates at BIDV declined by 10 Vietnamese dong, buying the greenback at 23,300 Vietnamese dong per U.S. dollar and selling at 23,380 Vietnamese dong per U.S. dollar.

This week, the reference exchange rates have seen two ups and three downs with total magnitude of 8 Vietnamese dong and 6 Vietnamese dong, respectively.

According to the central bank, as of June 11, the reference exchange rate rose 0.63 percent against the end of 2017, while the average rate offered by commercial banks advanced 0.47 percent.