Borussia Dortmund failed to keep pace with Bundesliga leader Bayern Munich as a last-gasp goal saw it held 2-2 by Darmstadt at Signal Iduna Park.

Thomas Tuchel's men went into the game five points behind Bayern, which it faces next weekend, and was searching for a win after its midweek draw with Hoffenheim had ended its perfect start to the campaign.

However, Dirk Schuster's men had already taken four points from trips to Schalke and Bayer Leverkusen this season and looked ready to cause another upset when Marcel Heller opened the scoring with a sublime volley.

But the in-form Pierre-Emerick Aubameyang looked to have turned the game on its head and secured the win for Dortmund, becoming the first player in Bundesliga history to net in each of the first seven games of a new season with a pair of goals putting his side ahead with less than 20 minutes remaining.

Aubameyang's goal-scoring run in the league now stretches back nine games into 2014-2015, a sequence which has seen him net 11 times.

However, Darmstadt spoiled the Gabon international's party as Aytac Sulu fired in an equaliser as Dortmund failed to clear a set-piece in the final minute of normal time.

Tuchel came in for criticism for leaving Henrikh Mkhitaryan out of the starting line-up against Hoffenheim, and, on his return, the Armenian quickly displayed his qualities by firing narrowly wide from 20 yards inside eight minutes.

Dortmund controlled possession but was struggling to carve open Darmstadt, and the visitor punished them with a swift counter-attacking move in the 17th minute.

Konstantin Rausch slid a pass down the left for Jerome Gondorf, and he picked out Heller who fired an exquisite first-time volley into the bottom-left corner.

The host should have pulled level three minutes later, but Aubameyang failed to put Marco Reus's cross into the back of the gaping net from inside the six-yard box. 

With Darmstadt defending deep and in numbers, Dortmund was forced to look wide or shoot from distance – Julian Weigl's tame 25-yard strike was the best it could muster before the interval.

It was a theme that continued in the second period, with the visitor remaining narrow and finding it difficult to get out of its own half.

With an hour on the clock, Mkhitaryan wriggled away from Heller but saw his shot batted away by Christian Mathenia.

Three minutes later, though, the equaliser finally came as Aubameyang peeled of his marker to supply the finish from Matthias Ginter's cross.

The talismanic Aubameyang was at it again with 19 minutes left on the clock, latching onto substitute Adnan Januzaj's deflected pass to get on the scoresheet yet again.

However, the headlines were stolen by Darmstadt centre-back Sulu, who picked out the bottom-left corner when a long free-kick fell to him on the edge of the area in the 90th minute.

Dortmund is subsequently four points adrift of league leader Bayern ahead of the crunch clash at the Allianz Arena on Monday (AEST).