Crude prices are having one of their best days in a year, rallying as much as 5% amid concerns that icy weather in the oil patch will crimp domestic supply, while tighter sanctions on Russia and Iran may eliminate barrels from global markets.

The U.S. Treasury Department is sanctioning Russian oil companies, tankers, officials and executives. Oil prices jumped on worries that crude supplies would face disruptions. Oil prices jumped more than 3% on Friday as the U.

The document, purported to be from the U.S. Treasury, was being circulated among traders in Europe and Asia. Reuters could not verify the veracity of the document

Oil prices jumped more than 4% on Friday, with global benchmark Brent breaking $80 per barrel for the first time since October on fears that tougher U.S. sanctions on Russia will disrupt crude supplies.