The statement from Vietnam's central bank banned credit institutions from trading in bitcoin and warned citizens not to invest in the currency.

Vietnam banned the virtual currency bitcoin, citing its ease of use for criminal purposes and its high risk for investors.

“Transaction by bitcoin is highly anonymous so bitcoin can become a tool for crimes like money laundering, drug trafficking, tax evasion, illegal payment,” the central bank said in a statement issued late on Thursday.

The statement banned credit institutions from trading in bitcoin and warned citizens not to invest in the currency.

“The price of bitcoin fluctuates over a short time so investments in bitcoin are risky,” Vietnam’s state bank said.

It did not outline punishments for violations of the ban. Online access to several popular bitcoin trading sites overseas appeared to be blocked.

The sudden closure of one of the largest bitcoin exchanges this week in Japan has raised concerns about the future of the digital currency.

Earlier this year several Vietnamese companies posted on their websites that they accepted bitcoin payments, according to local media reports.