Sayoc appeared in a courtroom before a US federal judge in Manhattan where he pleaded guilty, NBC News New York reported on Thursday evening.
The 57-year-old Floridian pleaded guilty to 30 charges, including using weapons of mass destruction, interstate mailing of explosives and use of destructive devices during crimes of violence.
READ MORE: US Mail Bombing Suspect Charged in 30-Count Indictment — Justice Department
The authorities initially charged Sayoc with five counts of criminal wrongdoing.
Sayoc is accused of sending packages containing explosive devices to numerous Democratic officials, including former President Barack Obama, former Vice President Joe Biden, former Secretary of State Hillary Clinton, US Congresswomen Deborah Wasserman Schultz and Maxine Walters, as well as to the corporate media outlet CNN.