US national security officials say Iran was responsible for sending threatening emails to Democratic voters ahead of next month’s presidential election.
Mr Ratcliffe also said US officials found Iran and Russia had obtained “some voter registration information”.
“Iran’s strong rejection of American officials’ repetitive, baseless and false claims was conveyed to the Swiss ambassador [who represents US interests in Tehran],” Iranian foreign ministry spokesman Saeed Khatibzadeh told state TV.
Kremlin spokesman Dmitry Peskov told the BBC: “We think this is unfortunate. These accusations come every day, they are all completely groundless, they are based on nothing.”
“They are most likely some sort of internal political process connected with the upcoming elections.”