New-signing Shinji Okazaki of Japan netted in Mainz 05's 3-2 home win over his ex-club VfB Stuttgart on Sunday in the Bundesliga -- having only left them last month.

Both defending champions Bayern Munich, who beat Moenchengladbach 3-1 on Friday, and Borussia Dortmund, who won 4-0 at Augsburg on Saturday, picked up wins on the opening weekend of the new season.

Mainz also opened their account with a convincing victory as Germany midfielder Nicolai Mueller netted goals either side of Okazaki's 65th-minute strike.

Mueller scored his first after just 14 minutes, but Bosnia striker Vedad Ibisevic levelled just two minutes later.

Japan's Okazaki, joined Mainz on July 1 in a three-year deal after two years at Stuttgart, and slotted home his team's second when he converted a cross from Czech Republic defender Zdenek Pospech before Meuller made it 3-1, 12 minutes from time.

Stuttgart's Martin Harnik gave his side hope with eight minutes left to make it 3-2, but hosts Mainz hung on while later on Sunday, Schalke host Hamburg.

Okazaki joined South Korea's Heung-Min Son of Bayer Leverkusen and Gabon's Pierre-Emerick Aubameyang who also scored on their debuts over the weekend.

Dortmund's new-signing Aubameyang hit a hat-trick as Champions League finalists Dortmund routed Augsburg 4-0 on Saturday.

The 24-year-old Gabon forward showed why Dortmund paid French League Cup winners St Etienne 13 million euros (US$17.3m) for him as he became the sixth player in Bundesliga history to hit three goals on his debut.

Poland striker Robert Lewandowski converted a penalty in the dying stages to complete Augsburg's misery at home.

South Korea's Son also scored on his first competitive appearance for Champions League hopefuls Bayer Leverkusen in their 3-1 win at home to Freiburg.

Germany striker Stefan Kiessling put the hosts ahead with 22 minutes gone, but Freiburg's new signing Mike Hanke levelled just before the break.

Son restored Leverkusen's lead just two minutes into the second half when he fired home from close range after a final pass from Sidney Sam.

Germany midfielder Sam then converted Kiessling's cross to seal the win with 52 minutes gone, while Leverkusen goalkeeper Bernd Leno protected his side's lead when he saved a 67th minute penalty from Jonathan Schmid.

Hertha Berlin marked their return to the top-flight after a year's absence with a stunning 6-1 rout of Eintracht Frankfurt.

Colombia striker Adrian Ramos and Tunisia forward Sami Allagui each scored twice in the hammering at Berlin's Olympic Stadium while a first-half penalty from Eintracht Frankfurt midfielder Alex Meier was all the guests could muster.

Hanover 96 enjoyed a 2-0 win over Wolfsburg, who finished with nine men after both midfielder Maximilian Arnold and Swiss defender Timm Klose were sent off.

Hoffenheim were held to a 2-2 draw at home to Nuremberg while Werder Bremen edged newly-promoted Eintracht Braunschweig 1-0 with Austria midfielder Zlatko Junuzovic hitting the 82-minute winner.