BERLIN, Jan. 18 (Xinhua) -- Second division outfit St. Pauli advanced into the quarterfinal after flabbergasting cup holder Borussia Dortmund 2-1 in German Cup's last 16 on Tuesday.

The hosts started brightly into the encounter and shocked the "BVB" with only four minutes gone when Etienne Amenyido benefitted on Marcel Hartel's square pass from very close.

Dortmund immediately took over and should have scored with 18 minutes played but Marco Reus couldn't mark the equalizer with only St. Pauli goalkeeper Dennis Smarsch to beat.

Haaland created the next promising chance but pulled wide the subsequent corner from a promising position.

The hosts defended well and were able to double the advantage just before the break as Axel Witsel cleared Guido Burgstaller's cutback pass into the wrong goal.

After the restart, St. Paul again caught the better start as Dortmund goalkeeper Gregor Kobel had to defuse Burgstaller's dangerous header on target in the 54th minute.

Dortmund however was able to halve the deficit in the 59th minute as Haaland caught Smarsch on the wrong foot after converting the handball penalty into the bottom right corner.

It remained Dortmund's only goal as St. Pauli's defense stood firm to clinch the ticket for the next round.

"It is a bad day for us. We woke up too late. St. Pauli played very well. It is really bitter to crash out as the titleholder," Dortmund's midfielder Marco Reus said.

"We didn't start well. We made our life difficult because we weren't there from the starting whistle. We then swallowed an own goal which didn't make things easier either," Dortmund's head coach Marco Rose said.

Elsewhere, second division club Hamburg book its place in the quarterfinals as well as the "HSV" overpowered Cologne 4-3 (1-1) in the penalty shootout.

Bochum bounced back from one goal down and eliminated Mainz 3-1 by courtesy on Milos Pantovic's second-half brace while Karlsruhe edged 1860 Munich 1-0.