Pierre-Emerick Aubameyang has labelled Borussia Dortmund CEO Hans-Joachim Watzke a "clown' in response to his dig at the Arsenal star earlier this week.
Aubameyang spent five years at Westfalenstadion before securing a £60 million ($74m) switch to Emirates Stadium in 2018.
The 30-year-old has since emerged as one of the most prolific strikers in the Premier League, netting 39 goals in 56 appearances.
In a recent interview with Suddeutsche Zeitung, Dortmund chief Watzke aimed a dig at Aubameyang, insisting his decision to join Arsenal was purely based on financial gain.
He cited BVB's consistent presence in the Champions League as proof of that fact, a competition that the Gunners have not participated in since 2017.
Aubameyang has hit back at Watzke on social media on Thursday, referencing former team-mate Ousmane Dembele's transfer to Barcelona while threatening to reveal the real reason behind his move to north London.
The Gabon international said: "Better for you, I never talk about why I really left Dortmund Mr Watzke you such a clown.
"I remember that time you said we never gonna sell Ousmane then you saw more than €100m,you were the first to take that money.
"Don't talk about money, please!!! Leave me alone, please!!!."
The Gunners sit top of Group F on goal difference at the moment, having picked up an impressive 3-0 win over Eintracht Frankfurt in Germany last time out.
Unai Emery's men will be expected to pick up another three points against Belgian opposition on Thursday, before resuming their Premier League campaign at home to Bournemouth on Sunday.
Aubameyang is likely to feature in both matches, with strike partner Alexandre Lacazette still out of action recovering from injury.
The Gabon frontman has scored eight goals in eight appearances this term, helping the Gunners rise to fourth in the Premier League.