(Reuters) - The San Francisco Giants completed a three-game sweep of the Los Angeles Dodgers with an 8-4 victory on Wednesday to move further clear of their National League West rivals going into the closing weeks of the regular season.

The Giants (69-55) entered the series trailing the Dodgers (67-58) by half a game in the division but left Los Angeles riding high with a 2 1/2-game advantage.

Matt Cain (13-5) controlled the series finale and the Dodgers' offense, tossing seven innings and allowing just one run to win his third straight start.

Joaquin Arias homered in the first inning to give the visitors a 3-0 lead, as he finished 3-for-5 with five RBIs, and San Francisco held a healthy 8-1 advantage before surrendering three late runs that flattered the hosts.

(Writing by Jahmal Corner in Los Angeles; Editing by John O'Brien)