Oil futures rose sharply early Friday, trading at their highest since October with support tied to cold weather in the U.S. and elsewhere and supply concerns.

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.

Oil prices declined for a second day on Thursday after large builds in fuel inventories in the U.S., the world's biggest oil user, though expectations for increasing winter fuel demand and concerns over tighter supply limited the drop.

U.S. crude oil inventories fell for a seventh consecutive week, while product stocks saw large builds last week as refineries increased their capacity use.