With his third victory in as many games, Prasanna remained a part of the six-player leading the tournament with a perfect score here at the black sea resort.
The Indian shares the lead with top seed Constantin Lupulescu of Romania, Bulgarian duo of Boris Chatalbashev and Vasil Spasov, veteran legendary Grandmaster Evgeny Sveshnikov of Latvia and Sandro Mareco of Argentina.
Meanwhile, Swapnil Dhopade and Ashwin Jayaram share the seventh spot on 2.5 points each along with 20 other players after draws in their third round game.
Highest rated Indian it the fray, Abhijeet Gupta yet again conceded a half point when he could not force mattes against young Israeli Asaf Givon and had to split the point.
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Sagar Shah, who had raised visions of an IM norm performance in the previous round, met his nemesis in Vitaliy Bernadskiy of Ukraine, while N Raghavi came up with an impressive game to beat Metodi Stoinev of Bulgaria.
Prasanna played energetically with black pieces to score an important victory. Anurag Mahamal went for the Ruy Lopez opening showing willingness for a complicated battle but his plans went awry after he missed a tactical shot that left his queen hanging in black's territory.