Vietnam's central bank on Thursday adjusted its reference exchange rate between Vietnamese dong and U.S. dollar up by 15 Vietnamese dong to 22,406 Vietnamese dong per dollar.

With the current trading band of plus or minus 3 percent, the ceiling exchange rate is 23,075 Vietnamese dong per dollar, and the floor rate is 21,739 Vietnamese dong per dollar, said the State Bank of Vietnam.

Major commercial banks in Vietnam, including Vietcombank and Vietinbank, have kept their exchange rates unchanged.

The country kept foreign exchange rates fairly stable in 2017. According to Vietnam's National Financial Supervisory Commission, the central exchange rate in late 2017 increased around 1.6 percent against early 2017, while the average rate offered by commercial banks dropped 0.2 percent, and that on the free market declined some 1.5 percent.

Vietnam's foreign reserve has now hit an all-time record high of 53 billion U.S. dollars, according to the central bank on Jan. 10. The reserve rose by nearly 11 billion dollars from mid-2017 and by roughly 12 billion dollars from late last year.