Sofia City Prosecutor's Office has submitted a formal request that Russian-French citizen Nikolai Kobliakov remain in detention.
Kobliakov, a businessman known to be a critic of Russian President Vladimir Putin, was arrested at the Sofia Airport on July 31, but was freed three days later.
The Sofia City Court then ruled the charges against him did not constitute a criminal offense.
A month on, however, a demand for his extradition issued by Russian authorities has arrived in Bulgaria, according to the website Dnevnik.bg.
The court is due to sit later on Monday to decide whether Kobliakov is to be taken into custody.