A 45th-minute goal from Shinji Kagawa saw Juergen Klopp's Dortmund extend their unbeaten league run to 15 matches with a 1-0 victory at home to Bayer Leverkusen.

Japan midfielder Kagawa fired home from a tight angle on the stroke of half-time, his fourth goal from as many games in all competitions.

But the champions remain just two points clear after Bayern registered a 2-0 victory at home to Kaiserslautern.

Mario Gomez struck his 18th league goal of the campaign, getting to the near post and turning in a cross from Franck Ribery on six minutes.

Jupp Heynckes' men looked the better side throughout the encounter and got a deserved second when Thomas Mueller headed in a Toni Kroos free-kick on the half-hour.

Later, Borussia Moenchengladbach returned to third place, three points back from Dortmund, courtesy of a comprehensive 3-0 win at home to Schalke, who drop to fourth.

Marco Reus eluded defender Benedikt Howedes to open the scoring with a shot past Schalke goalkeeper Lars Unnerstall just two minutes into the match at Borussia-Park.

Mike Hanke rounded off a flowing move to double the lead in the 15th minute.

And Venezuela international Juan Arango ended the match as a contest after just 32 minutes, when he made it 3-0 from a well-worked indirect free-kick.

Elsewhere, Markus Babbel was almost given a dream start as Hoffenheim boss before his side conceded late to draw 1-1 at Werder Bremen.

Dane Jannik Vestergaard netted after a Sebastian Rudy corner in the fourth minute, giving the visitors an ideal start.

But Austrian striker Marko Arnautovic struck late in the encounter for Bremen.

Stuttgart bounced back from Wednesday's DFB Pokal loss to Bayern Munich with a 5-0 thrashing of Hertha Berlin.

Austria forward Martin Harnik's hat-trick, and goals from Vedad ibisevic and Shinji Okazaki, led Stuttgart to the resounding win.

Elsewhere, Mohamed Zidan and Artur Sobiech exchanged goals as Mainz and Hannover played out a 1-1 draw.