(Reuters) - The San Francisco Giants kept alive their post season by claiming a 2-1 win in 10 innings against the Cincinnati Reds on Tuesday after losing the first two games of the best-of-five Division Series.

A two-out error by eight-time Gold Glove-winning Reds' third baseman Scott Rolen on a grounder by Joaquin Arias allowed Buster Posey to score from third base in the 10th after he had moved up on a passed ball by catcher Ryan Hanigan.

The Giants, World Series winners in 2010, were held hitless by Cincinnati starter Homer Bailey until a two-out single in the sixth by second baseman Marco Scutaro. They had tied the game 1-1 in the third inning without benefit of a hit on a hit batsman, a walk, a sacrifice bunt and a sacrifice fly.

Game Four will be in Cincinnati on Wednesday.

(Reporting by Larry Fine in New York, Editing by Greg Stutchbury)