Bayern Munich suffered a jolt to their title defence, losing their first league game of the season 5-1 in Frankfurt on Saturday while RB Leipzig triumphed 3-2 at 10-men Borussia Dortmund.

In a wet and wild contest in Frankfurt, the hosts raced into an extraordinary 3-0 first-half lead, with Omar Marmoush, Junior Dina Ebimbe, and Hugo Larsson scoring the goals as Dino Toppmoeller's side outmuscled a timid Bayern.

Joshua Kimmich dragged Bayern back into the match just before half-time but French midfielder Ebimbe had other ideas, capping a scintillating counter-attack after a mistake by Dayot Upamecano to make it four.

Ansgar Knauff added a fifth to put the game out of reach for Thomas Tuchel's side to complete a memorable performance for Frankfurt, who become the first team to score five goals against Bayern in the first 60 minutes of a league game since Frankfurt themselves, in 1975.

A stunned Tuchel said after the game that his side were punished by a Frankfurt team who were callous in front of goal.

"We didn't defend consistently and were punished mercilessly today," Tuchel told German broadcaster ARD.

"That's why this result is very difficult to digest on the scoreboard. We deserved to lose. Not 5-1, but we deserved to lose. That is the bottom line."

Leaders Bayer Leverkusen retain their three-point cushion and travel to third-place Stuttgart on Sunday on a weekend when six of the Bundesliga's top seven face each other.

In a game contested between two sides in the chasing pack, Leipzig beat Dortmund in an absorbing contest at Signal Iduna Park.

Dortmund were dealt an early blow with Mats Hummels' red card, which denied the visitors a penalty but they went on to take the lead in the 32nd minute through a Ramy Bensebaini own goal.

Ten-man Dortmund clawed their way back into the contest through Niklas Suele's close-range finish on the stroke of half-time - but Leipzig's Austrian forward Christoph Baumgartner tapped in to put Leipzig back in front early in the second half.

Yussuf Poulsen struck as the clock ticked into injury time to make it three goals and three points, keeping Leipzig fourth and opening a gap of four points to fifth-placed Dortmund, despite Niclas Fuellkrug's late header briefly giving Dortmund hope.

"These were important three points today. Very hard-earned. Really hard for the coach too. It's difficult to analyse emotionally," Marco Rose, formerly the coach of Dortmund, and now in charge of Leipzig, told ARD.

A despondent Dortmund coach Edin Terzic referenced the red card for Hummels as the game's turning point: "It's not easy to play against RB Leipzig, especially when you're outnumbered. You saw that we got off to a really good start, were very dominant... after the red card it was a completely different game."

Terzic acknowledged that Dortmund, who have only one win in their last six Bundesliga games and slipped off the pace in the top four race, are going through a rough spell.

"It's a very difficult phase we're going through at the moment. It's not easy to answer similar questions on the microphone every three days."

Union Berlin won their first game since August 26 with a 3-1 victory over Borussia Moenchengladbach ensuring a winning start in the Bundesliga under new coach Nenad Bjelica.

The Croatian boss ran down the touchline to join the celebrations with his players as the team climbed to 15th.

Elsewhere, Werder Bremen arrested a four-game winless slump with a 2-0 win over Augsburg, secured by Niklas Stark's first-half strike and Marvin Ducksch's, midway through the second

Heidenheim edged out Darmstadt with a 3-2 win in a meeting of two of the newly-promoted strugglers. Jan Schoeppner scored twice for Heidenheim, which leaves Darmstadt winless in seven Bundesliga games.