(CNN) Former Tennessee Gov. Phil Bredesen's Senate campaign told the FBI in a letter Thursday that it fears it was hacked.

The revelation comes as intelligence experts predict a widespread threat of cyberattacks on campaigns and election systems from both domestic and foreign hackers.

According to a copy of the letter obtained by CNN, Bredesen's campaign "received multiple emails that appeared to be from the campaign's media buyer" on February 28, which included specific details about a planned media buy and "urged the campaign to wire funds to an international bank account."

The letter, written by the campaign's counsel Robert Cooper and sent to the FBI's Memphis division, also detailed another email received on the same day which "purport(ed) to be from a principal in the media team that produced the TV commercial, urging transfer of the funds."

An FBI official confirmed that the Memphis field office received the letter but declined to comment further.

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