South Korea’s cryptocurrency exchange Bitsonic Thursday filed a lawsuit against Shinhan Bank for freezing its account.

The bank said it banned the exchange from accepting deposits a sudden and unusual jump in trading.

A Shinhan Bank spokesman said the freezing came out of “our concern over the possibility of money laundering.”

The exchange immediately filed a preliminary injunction against the decision. BItsonic claimed that it would nullify what it calls the bank’s arbitrary decision.

Last year, the court asked the Nonghyup Bank not to suspend an account with another exchange Coinis.

South Korean banks are quite sensitive to cryptocurrency trading.

Some exchange executives suspect that Shinhan Bank acted out of an instruction from the financial regulator.

However, the Korea Federation of Banks denied any instruction or whatsoever indication from the government about business with cryptocurrency exchanges.