According to the court document, Russian national Maria Butina has appealed the 18-month sentence in the US court.
"I, the above named appellant, hereby appeal to the United States Court of Appeals for the District of Columbia Circuit from the above-stated judgment," Butina said in the document.
On 26 April, a US federal court sentenced Butina to 18 months in prison after she pleaded guilty to a single count of conspiring to act as an unregistered foreign agent. Butina, who signed her plea deal after being held for unusually lengthy periods of time in solitary confinement, had requested a sentence of time served.
The Russian Embassy in the United States said in November that the US authorities had kept Butina in a single cell under solitary confinement for 67 days, exceeding the limit recommended by the Nelson Mandela Rules for the treatment of prisoners.
READ MORE: Russia's Maria Butina Transferred to US Norther Neck Jail in Virginia — Lawyer
Russian President Vladimir Putin has said that Butina's indictment is unjustified because she was not tasked to perform any mission on behalf of the Russian government.
Butina could be released as early as 5 November if her sentence is shortened for good conduct.