San Francisco, CA -- (Sports Network) - Bengie Molina went 2-for-3 with two home runs, and Barry Zito tossed six solid innings, as San Francisco topped Washington, 6-3, in the first of three games with the Nationals.

Zito (5-12) won his second consecutive decision for the first time this season after allowing only three runs on seven hits and three walks with five strikeouts.

Fred Lewis added a solo homer, while Aaron Rowand and Omar Vizquel each drove in a run for the Giants, who snapped a three-game losing streak.

Jason Bergmann (1-7) gave up five runs - four earned -- on five hits in five innings to absorb the loss. He has lost his past six decisions, and has not won since a May 15 outing against the Mets.

"(Bergmann) fell behind in the count and they got good pitches to hit and they hit them out," Nationals manager Manny Acta said. "I'm not going out there thinking that he's going to give up a bunch of long-balls because he's a fly ball pitcher."

Paul Lo Duca finished 2-for-4 with two RBI, while Willie Harris went 2-for-5 and batted in a run for the Nationals, who had a two-game win streak snapped. Ryan Zimmerman, who had been on the disabled list since May 26, was activated on Tuesday and went 1-for-3 with a pair of walks.

The Giants got to Bergmann right away, as Lewis homered to start the bottom of the first. Later in the inning, after Eugenio Velez reached on an infield single, stole second and advanced to third on a fly out, Molina blasted a two- run shot to center field for a 3-0 lead.

In the second, Washington's Jesus Flores tripled and Lo Duca chased him home with a double. The Nationals got within a run in the fourth when Lo Duca again plated the run, on an infield single that scored Austin Kearns.

But San Francisco pulled further ahead in the fourth, when Molina led off with a homer, his eighth of the season. After two fly outs, Rich Aurilia reached base on Felipe Lopez's throwing error, and then scored when Vizquel doubled.

"To have a game like today, it doesn't say anything about how you're going to end up," Molina said. "But for sure it's a step forward, and for me it's a boost of confidence that I can do it again so hopefully I can keep going."

Harris homered to begin the fifth, bringing Washington within 5-3, but Zito held the Nationals scoreless from there until the end of the sixth. Jack Taschner and Sergio Romo combined to pitch a scoreless seventh, while Tyler Walker threw a scoreless eighth.

Rowand's RBI single in the home eighth, plating Randy Winn, completed the scoring and Brian Wilson worked a scoreless ninth for his 26th save of the season.

Game Notes:

On Tuesday, the Nationals agreed to a two-year contract extension with shortstop Cristian Guzman through 2010. They also traded pitcher Jon Rauch to Arizona in exchange for infielder Emilio Bonifacio, who they then optioned to Triple-A Columbus. Lastly, Washington recalled pitcher Garrett Mock from Columbus...Attendance was 34,813...The Giants activated outfielder Dave Roberts from the 60-day disabled list on Tuesday, and recalled him from a rehab assignment at Triple-A Fresno. Roberts underwent arthroscopic left knee surgery on April 12 after playing in just six games, and batting .118 with one run batted in.