Jakub Blaszczykowski and Robert Lewandowski each scored twice for the defending champions, who joined Bayern and third-placed Schalke on 37 points.

Kevin Grosskreutz netted the opener after 16 minutes when he was picked out near the penalty spot by Shinji Kagawa, and the winger put a simple finish past Hamburg goalkeeper Jaroslav Drobny.

Lewandowski doubled their advantage eight minutes before the interval after a magnificent solo run through a static Hamburg defence, and when Blaszczykowski powered home a precise shot from outside the box in the 58th minute, Dortmund were as good as home.

Blaszczykowski's second came from the penalty spot, and Lewandowski made it five in the 83rd minute, although Jose Paolo Guerrero pulled back a consolation three minutes later.

Elsewhere on Sunday, Bayer Leverkusen posted a 3-2 win at home over struggling Mainz.

An own-goal from Zdenek Pospech put Leverkusen up at the BayArena, and they were looking comfortable when Manuel Freidrich doubled their lead after 35 minutes.

But Mainz turned the game on its head five minutes after half-time, with Eugen Polanski and Marco Caligiuri scoring within three minutes of each other to tie things up at 2-2.

It was left to midfielder Lars Bender to wrap up the three points for Robin Dutt's men, scoring the winner in the 70th minute.