The U.S. filed a civil forfeiture complaint on Monday against $61 million in cryptocurrency that the Justice Department claims is proceeds from sales of sanctioned Iranian crude oil and petroleum products. 

According to the complaint brought by the U.S. Attorney’s Office for the Southern District of New York, Iran used a network of cryptocurrency actors in China and elsewhere to launder more than $1.5 billion in illicit oil money intended to benefit the Iranian military. 

“By cutting off funds raised by the black-market sale of crude oil, the Iranian military and terrorists are weakened. The FBI will not relent in its resolve to drain the funds from dangerous foreign actors,” a statement from the office said. 

The complaint alleges that two Chinese companies, Blessed Trust and Hexa Whale, used trading accounts at the UAE-based cryptocurrency exchange Binance to launder the proceeds of black-market sales of Iranian oil, funneling the illicit funds to Iran, its agents, and proxies, where the funds were used to finance terrorist and other activities of the Iranian government.

A Binance spokesperson told CNBC that the company has "zero tolerance for sanctions violations or illicit activity," and it denied that it had permitted transactions with sanctioned individuals. It's cooperating with law enforcement, the spokesperson said.