Oneli's work on western Georgia's mining town Chiatura and its inhabitants impressed the judges of the documentary competition section and was distinguished with the Documentary Special Jury Award.
In addition, City of the Sun was honoured with the New Voices prize from the International Federation of Film Critics (FIPRESCI), to mark his maiden feature documentary.
Collecting the prizes for his work, the Georgian filmmaker went on stage of the festival along with Zurab Gelashvili, one of the protagonists of the documentary and a Chiatura resident.
They told the audience in Minsk about their stories, with Oneli explaining how he was captivated by photographs of Chiatura while living in New York and decided to travel back to his home country to film the city.
Known during the Soviet era as the supplier of about half of the world's manganese demand, Chiatura and its residents were hit with economic hardship since the dissolution of the USSR.
[W]ith drastically reduced manganese production, dangerous working conditions and little prospect for any improvement, it is well on its way to becoming a ghost town", said the film's summary for the Minsk festival.
Oneli spent three years filming in Chiatura and recording life stories of locals, with his final work noted for its cinematography and protagonists at festivals around Europe throughout this year.
Most recently, City of the Sun was distinguished with Best Documentary Film award at the Sarajevo Film Festival in August, while the documentary was also awarded at Sheffield Doc/Fest and DocumentaMadrid festivals.
Oneli's work is a co-production between Georgia, the United States, Qatar and the Netherlands and features screenplay by its director as well as filmmaker Dea Kulumbegashvili.
This year's Minsk International Film Festival ran from November 3-10 and featured over 200 screenings of films by directors from Europe.