Petric, who missed Hamburg's 1-1 Bundesliga draw with Schalke on Sunday due to a virus, put the visitors in front after 15 minutes.

Fellow Croatian Ivica Olic doubled Hamburg's advantage just before halftime.

Emile Rilke pulled one back nine minutes past the hour mark but Hamburg held onto their lead to claim an important victory.

Another German team, Schalke, enjoyed a winning start to their group A campaign.

They beat French side Paris Saint-Germain 3-1 at home, thanks to an own goal from Larrys Mabiala and two strikes from Kevin Kuranyi and Halil Altintop.