Mueller has stated that he is resigning from the US Justice Department after the conclusion of the Russia investigation.
"We are formally closing the Special Counsel's Office and as well I'm resigning from the Department of Justice to return to private life", Mueller said during the press conference.
He continued by saying that charging US President Donald Trump was not an option that he could consider under Justice Department guidelines.
According to Mueller, it is "inappropriate" for him to testify further on the Russia probe.
Russia has repeatedly denied any claims of interference in the US political system, stressing that the allegations were made up to excuse the election loss of Trump's 2016 opponent Hillary Clinton, as well as to deflect public attention from actual instances of election fraud and corruption.