US authorities on Friday unveiled charges against 10 Iranians for allegedly evading American sanctions on Tehran by concealing more than $300 million in transactions over 20 years through front companies.

The individuals are believed to have conducted transactions on behalf of the Iranian government, including purchasing two $25 million oil tankers, through more than 70 front companies in the United States, Iran, Canada, the United Arab Emirates and Hong Kong, the Justice Department said in a statement.

The suspects, who were also slapped with a money-laundering fine of more than $157 million, are believed to be outside the United States.

"Through the use of front companies, money service businesses and exchanges throughout the world, the defendants worked to disguise hundreds of millions of dollars' worth of transactions on behalf of a state sponsor of terrorism," John Demers, assistant attorney general for national security, was quoted as saying.

"Make no mistake, the Department of Justice will continue to deploy all tools necessary to curb the Iranian regime's ability to use the US financial system to support its malign endeavors," he said.

If convicted of the conspiracy charge, the defendants face a maximum sentence of 20 years in prison. 

Iran is subject to US economic sanctions, with previous president Donald Trump aggressively using the measures to punish the Islamic republic.