Shinji Kagawa led Borussia Dortmund to a 6-1 win at Cologne to extend his side's unbeaten run to 21 games and restore its five point lead in the Bundesliga yesterday.

Kagawa scored two goals and helped set up two more as Dortmund delivered a devastating second-half performance to leave Cologne one point above the relegation zone.

The win also issues a statement of intent after Bayern Munich had cut the gap at the top of the table to two points on Saturday. There are seven games remaining in the title race.

Cologne took the lead in the 13th minute when Martin Lanig sent in a long cross for Milivoje Novakovic to head beyond Dortmund goalkeeper Roman Weidenfeller.

Lukasz Piszczek equalized 13 minutes later when he rose unopposed to meet Marcel Schmelzer's free kick with a glancing header.

Lukas Podolski might have scored in the 38th, when he found himself alone in front of Weidenfeller, but the Dortmund defense managed to scramble back in time.

Sven Bender had a goal ruled out for offside in the 41st, as Dortmund began to turn the screw.

Kagawa fired the visitors in front two minutes into the second half with a superb volley from a narrow angle in off the underside of the crossbar.

Wonderful play from Kagawa helped create Dortmund's third in the 52nd, when the Japan midfielder dragged the ball back for Jakub Blaszczykowski to play across goal, leaving Robert Lewandowski and Grosskreutz the simple task of deciding who should score. Lewandowski tapped it in for his 17th goal of the season.

Ilkay Guendogan played a one-two with Kagawa to score Dortmund's fourth in the 79th, before Piszczek crossed for Kagawa's 11th goal of the season a minute later.

Dortmund coach Juergen Klopp took the Japan star off immediately afterward, but there was no let up for the home side with Ivan Perisic adding another goal in the 84th.

Earlier, Cacau earned Stuttgart a lucky 1-0 win over Nuremberg to move his side up to seventh, likely the last Europa League qualification place.

Cacau scored out of nothing in the 78th minute when the Brazil-born Germany striker took Martin Harnik's return pass before slotting coolly inside the left post.

Nuremberg had missed a host of chances to score and earned 14 corners compared to four for Stuttgart.

Adam Hlousek hit the crossbar in the seventh minute, former Nuremberg player Julian Schieber cleared Markus Feulner's effort off the line a minute later, and United States defender Timmy Chandler hit the post.

"We were clearly the better team," said Daniel Didavi, a former Stuttgart player, after his side's third defeat in a row. "Stuttgart attacked once and scored, and we're left there with empty hands."

Due to the German Cup final being played by Bundesliga leader Borussia Dortmund and second-place Bayern Munich, seventh place in the league will likely include a Europa League place.