Milivoje Novakovic opened the scoring to give Cologne a surprise 13th-minute lead at RheinEnergieStadion.

Juergen Klopp's men drew the game level prior to half-time through Lukasz Piszczek, before they ran rampant after the break.

Shinji Kagawa netted a brace to go with strikes from Ilkay Gundogan, Robert Lewandowski and Ivan Perisic to seal an impressive victory.

Dortmund were made to pay for a sloppy start when a Martin Lanig cross found Novakovic, who sent a looping header over Roman Weidenfeller.

The visitors equalised in the 26th minute when Marcel Schmelzer picked out Piszczek with a lovely cross, and the Poland international applied a skilful header to beat Michael Rensing.

Dortmund dominated the second half and Kagawa started the rout when he gave his side the lead with a powerful volley that cannoned in off the bar.

The Japan international was involved in Lewandowski's goal, releasing Jakub Blaszczykowski, who squared for the striker to apply a simple finish.

They made it 4-1 when a superb one-two between Kagawa and Gundogan split open the Cologne defence.

Gundogan was left to easily convert to pile more misery on Stale Solbakken's team, before Kagawa completed his brace by poking home a Piszczek cross and Perisic put the icing on the cake with Dortmund's sixth.

In the day's other game, Stuttgart extended their unbeaten run to five matches with a 1-0 win over Nuremberg.

Cacau scored the only goal of the encounter in the 78th minute, collecting a Martin Harnik pass before placing into the bottom corner.

Nuremberg missed several chances throughout the contest, and were unable to make anything out of their 14 corners.