The FBI secured a warrant last year to monitor the communications of Carter Page, a former election campaign adviser to President Donald Trump, the Washington Post reported on Tuesday.
Page, who was previously a former investment banker in Moscow, was believed to have acted "as an agent of a foreign power, in this case Russia," U.S. officials told the newspaper.
The Foreign Intelligence Surveillance Act (FISA) warrant was one of the strongest pieces of evidence that indicated a Trump adviser was in touch with Russian agents during the 2016 presidential campaign, the Washington Post said.
Page has denied any wrongdoing, according to the report.
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