Defending Bundesliga champions Borussia Dortmund moved to within three points of current leaders Bayern Munich with an emphatic 5-0 win over Cologne in a one-sided game at the Westfalenstadion. Shinji Kagawa opened the scoring for the dominant hosts in the seventh minute and Marcel Schmelzer added the second after 25 minutes. Robert Lewandowski scored just before and just after the break, while Sebastian Kehl rounded off the scoring in the 66th minute. After a dismal display, Cologne could have no complaint about a result that takes Dortmund into second place. A physical start to the game with plenty of fouls was punctuated by the opening goal. Kevin Grosskreutz raced into the area to reach Mats Hummels\' lobbed pass and pull the ball back for Kagawa to open the scoring. Kehl\'s 20-yard shot in the 15th minute had Michael Rensing at full stretch and it was clear that Dortmund were eager to put their midweek UEFA Champions League disappointment behind them. They doubled their lead in the 25th minute when Cologne failed to clear their lines and the ball finally fell to Schmelzer, who placed his shot into the top right-hand corner of the goal from just inside the penalty area. The one-sided nature of the game continued, with Grosskreutz denied by Rensing in the 43rd minute before Lewandowski scored their third just before the break. Sven Bender squared the ball for the in-form Polish international, who stuck out his leg to score his fifth goal in four games for his club. That record became six in four - as well as two goals in successive internationals - after just five minutes of the second half when Lewandowski latched onto Grosskreutz\'s header to beat Rensing from ten yards out. Kehl added the fifth in the 66th minute, heading in powerfully from Jakub Blaszczykowski\'s cross from the goal line. Dortmund had chances to score even more, but Rensing limited the damage for the visitors, who never even tested Dortmund goalkeeper Roman Weidenfeller.