The United States on Thursday slapped economic sanctions on four petroleum firms that US officials accuse of moving oil exports for the Quds Force of Iran's Revolutionary Guards.

The new sanctions come three weeks after the US killing of the Quds Force commander Qasem Soleimani in a missile strike that Washington claimed was preemptive.

"Iran's petrochemical and petroleum sectors are a primary source of funding for the Iranian regime's global terrorist activities and enable its persistent use of violence against its own people," Treasury Secretary Steven Mnuchin said in a statement.

Washington has recently also targeted other Iranian entities in the commodities, including metals companies and oil companies accused of supporting the Revolutionary Guards.

The firms targeted Tuesday are Triliance Petrochemical Co Ltd and Sage Energy HK Limited, both in Hong Kong, Peakview Industry Co Limited in Shanghai and Beneathco DMCC of Dubai.