BELGRADE, June 21 (Reuters) - The ruling Serbian Progressive Party (SNS) is set to win Serbia's parliamentary election on Sunday with 63.4% of votes counted, according to a projection by pollsters Ipsos and 온라인토토사이트 CeSID, based on a sample of the partial polling station count.

Socialist Party of Serbia is set to come second with 10.3% of votes, while a center-right Serbian Patriotic Alliance led by the former water polo player Aleksandar Sapic is projected to come third with 3.9% of the votes.

(Reporting by Ivana Sekularac and Aleksandar Vasovic; Editing by Edmund Blair)