Thomas Tuchel's Bayern Munich tenure started with a resounding 4-2 victory over rivals Borussia Dortmund at Allianz Arena.

Tuchel replaced Julian Nagelsmann during the international break, and his first game at the helm saw him tasked with shifting his former club Dortmund from top spot in the Bundesliga.

It was a fantastic start for Tuchel on the other side of the Klassiker rivalry, with Gregor Kobel's calamity and Thomas Muller's double putting Bayern 3-0 up inside 23 minutes.

Kingsley Coman nudged Bayern further ahead, though Emre Can's penalty and Donyell Malen's neat finish somewhat reduced the embarrassment for Dortmund, who lost in the league for the first time since November.

Bayern took the lead in bizarre fashion.

Dayot Upamecano's long throughball was seemingly running straight through to Kobel, but Dortmund's goalkeeper opted to try and boot it upfield, only to miscue, inadvertently sending the ball skimming into his own goal.

It was 2-0 just five minutes later, Matthijs de Ligt nodding a corner into the path of Muller, who stabbed home from close range.

Another Kobel blunder gifted Bayern a third – Muller on hand to tuck in the rebound after Leroy Sane's strike had been parried out.

Coman extended the lead in the 50th minute, latching onto Sane's clever pass to sidefoot into the bottom corner, and Dortmund had a reprieve when Eric Maxim Choupo-Moting's acrobatic finish was disallowed for offside.

Can smashed home a penalty after Jude Bellingham was felled by Serge Gnabry before Malen slotted in, but those goals were merely minor blips in an emphatic Bayern win.