Borussia Dortmund insisted that Chelsea target Pierre-Emerick Aubameyang was going nowhere after the Chelsea target scored twice in a 3-1 preseason win over AC Milan in China on Tuesday.

The coveted Gabon hitman showed just why Dortmund are so reluctant to part company with their star striker with two confidently taken goals in rain-lashed Guangzhou.

"We have decided that Auba will stay with BVB," said Dortmund's sporting director Michael Zorc. "The transfer window is closed for him."

Nuri Sahlin opened the scoring for Dortmund after 16 minutes following a period of sustained pressure, finding the net with a tidy side-footed shot after good work from American teen prodigy Christian Pulisic.

Aubameyang got on the scoresheet against his former club two minutes later when he slammed a penalty into the top left corner to double Dortmund's advantage after Pulisic had been tripped in the box.

AC Milan pulled one back on 23 minutes when Columbian forward Carlos Bacca unleashed a low shot from distance with the outside of his right boot which curled just inside the Dortmund post.

But the Germans effectively killed off the game in the 64th minute when Pulisic teed up Aubameyang to fire his second of the night as both teams continued to make a raft of second-half substitutions in the hot and humid conditions.

The transfer window in Germany closes at midnight (2200 GMT) on August 31, but director of sport Michael Zorc claimed it is effectively already shut for Aubameyang.

"We have decided that 'Auba' will stay with Borussia Dortmund. The transfer window is closed as far as he is concerned, because otherwise we would have run out of time (to find a replacement)," insisted Zorc.

Chinese side Tianjin Quanjian had also reportedly wanted to pay 80 million euros ($92.6m) for him, but with three years left on his Dortmund contract, the German club says Aubameyang is staying put.

New coach Peter Bosz, who has replaced Thomas Tuchel, unsurprisingly would want Aubameyang at Dortmund when the Bundesliga season starts on August 18.

"I am glad that he is in my team," said the Dutchman.

"He is an extraordinary player and he has shown that once more against Milan.

"He's a great bloke and a great footballer."