Finkevich is a member of Young Belarus, a group closely tied to opposition parties mobilizing for the country's 2011 presidential election.
After being robbed and beaten, Finkevich was found abandoned outside the capital, Minsk, with his hands tied behind his back.
Police are looking into the incident, which they say had nothing to do with Finkevich's political activities.
In May 2006, Finkevich was sentenced to two years under a "restricted freedom" regime for writing political graffiti. In late 2007, he had his sentence extended by another 18 months for violating the rules of his correctional facility.
On February 5 of this year, the court considered Finkevich's appeal, unexpectedly shortened his second term to six months, and released him.