Borussia Dortmund came from behind to beat Union Berlin 4-2 and remain unbeaten in the Bundesliga on Saturday, despite Leonardo Bonucci scoring his first goal for the capital club.

Italian veteran Bonucci put Union ahead from the penalty spot in a dramatic first-half, but Dortmund battled back to claim their fifth win of the season.

"We were really good today. I usually like to be critical, but I think we can be really proud of this performance," said Dortmund defender Mats Hummels.

Last season's surprise package Union have now lost their last seven in all competitions as they struggle with the step up to Champions League football in this campaign.

"It is really tough mentally to have to take so many hits. I think the international break will do us good," Union defender Robin Gosens told Sky.

Union's sloppy defending at set-pieces has been a major reason for their miserable run this autumn, and it continued to haunt them in Dortmund.

Having started brightly, the visitors allowed Niclas Fuellkrug to give Dortmund the lead at a corner on seven minutes.

Fuellkrug's joy was shortlived, however. Just two minutes later, he deflected a Robin Gosens header into his own net to make it 1-1.

The drama continued with three game-changing VAR decisions in the space of 10 minutes.

Union's Alex Kral and Dortmund's Fuellkrug both had headed goals ruled out for offside, before Mats Hummels conceded a penalty with a late challenge on Sheraldo Becker.

Bonucci converted with ease from 12 yards to grab his first Bundesliga goal and put Union in front.

Yet Dortmund struck back with two goals in quick succession just after half time.

First, Former Union player Nico Schlotterbeck whipped a breathtaking shot into the top corner from the edge of the area to level the scores.

Minutes later, substitute Julian Brandt tore through Union on the counter-attack to put Dortmund back in front.

The hosts sealed victory through another former Union player on 72 minutes, when Julian Ryerson's long-range shot was deflected in to make it 4-2.

- Guirassy hat-trick -

The win put Dortmund second overnight, while Stuttgart went top with a brilliant 3-1 win over Wolfsburg.

In-form Guinea striker Serhou Guirassy continued his brilliant run of form with a hat-trick as Stuttgart came from behind to grab their sixth win of the season.

Yannick Gerhardt put Wolfsburg in front with a cool finish midway through the first half.

But Guirassy converted a cool penalty in the second half before adding two more in the last 15 minutes to claim his second hat-trick of the season.

The Guinea international now has 13 goals from his first seven games, a new Bundesliga record at this stage of the season.

Elsewhere, RB Leipzig were left frustrated after a wasteful performance saw them draw 0-0 at home to Bochum.

Bochum goalkeeper Manuel Riemann saved two penalties either side of half time, denying both Xavi Simons and Emil Forsberg the chance to give Leipzig the lead.

Promoted side Darmstadt scored twice in the second half to clinch a 2-1 win away to Augsburg.

Tim Skarke's screamer and Tobias Kempe's penalty put Darmstadt ahead, and Ermedin Demirovic' late strike for Augsburg was not enough to deny the visitors a second win in two weeks.